Method and system for removing carbon dioxide

Abstract

Disclosed is a method of removing carbon dioxide from an exhaust gas of an offshore vessel having a plurality of ballast tanks. The method comprises: storing a lean solvent in at least one ballast tank from the plurality of ballast tanks; receiving, at an absorber, the lean solvent and the exhaust gas containing carbon dioxide; absorbing, via the lean solvent received by the absorber, carbon dioxide from the exhaust gas to generate a rich solvent containing the absorbed carbon dioxide; and storing the rich solvent generated by the absorber in at least one ballast tank from the plurality of ballast tanks. A system for removing carbon dioxide from the exhaust gas of the offshore vessel is also disclosed.

Description

METHOD AND SYSTEM FOR REMOVING CARBON DIOXIDETECHNICAL FIELD

[0001] The present invention relates to a method and a system for removing carbon dioxide from an exhaust gas of an offshore vessel.BACKGROUND

[0002] Carbon dioxide (CO2) is a greenhouse gas that is commonly contained in exhaust gases that are produced in a wide variety of combustion processes burning carbon based fuels. Solvent-based carbon dioxide capturing methods typically utilize a lean solvent in an absorber to absorb CO2 from a gas and release a gas with reduced level of CO2. The absorber subsequently generates a rich liquid solvent that contains CO2 absorbed from the gas. There remains a need for methods and systems to improve implementation of such solvent-based carbon dioxide capturing methods in an offshore vessel.SUMMARY

[0003] Examples of the present invention as described herein aim to address one or more of the problems described hereinabove.

[0004] According to a first aspect of the present invention, there is provided a method of removing carbon dioxide from an exhaust gas of an offshore vessel having a plurality of ballast tanks. The method comprises storing a lean solvent in at least one ballast tank from the plurality of ballast tanks. The method further comprises receiving, at an absorber, the lean solvent and the exhaust gas containing carbon dioxide. The method further comprises absorbing, via the lean solvent received by the absorber, carbon dioxide from the exhaust gas to generate a rich solvent containing the absorbed carbon dioxide. The method further comprises storing the rich solvent generated by the absorber in at least one ballast tank from the plurality of ballast tanks.

[0005] The method may facilitate removing carbon dioxide from the exhaust gas while enabling better use of the plurality of ballast tanks of the offshore vessel. Specifically,storing the lean solvent and the rich solvent in the plurality of ballast tanks may obviate a need to allocate extra storage space in the offshore vessel for storing the lean solvent and the rich solvent. It may further allow loading / bunkering a large volume of the lean solvent at once, which may allow the absorber to operate for a longer period of time during voyage of the offshore vessel. Further, the rich solvent and the lean solvent may be used in place of ballast water to ensure that traditional functionality of the ballast tanks (e.g., to provide hydrostatic stability) is not compromised. The method may thus allow the offshore vessel to safely carry more cargo while reducing emissions from the offshore vessel.

[0006] Optionally, the method further comprises storing at least one of the lean solvent and the rich solvent among the plurality of ballast tanks based on a density of the lean solvent and / or a density of the rich solvent. As the lean solvent and the rich solvent may have different densities, their densities may be important factors to consider while storing them in the plurality of ballast tanks. Storing the at least one of the lean solvent and the rich solvent among the plurality of ballast tanks based on the density of the lean solvent and / or the density of the rich solvent may facilitate obtaining an optimal weight distribution of the offshore vessel when a large volume of the lean solvent and / or the rich solvent is stored in the plurality of ballast tanks. Furthermore, storing the at least one of the lean solvent and the rich solvent among the plurality of ballast tanks based on the density of the lean solvent and / or the density of the rich solvent may enable maintaining a stability of the offshore vessel, as the actual mass (which is a function of density) of the lean solvent and / or the rich solvent may need to be considered for the stability and hull strength.

[0007] Optionally, the method further comprises storing the lean solvent into one or more of the plurality of ballast tanks based on a loading and a stability of the offshore vessel. This may ensure that the loading and the stability of the offshore vessel remain in accordance with acceptable loading and stability requirements of the offshore vessel, for example, when the lean solvent is loaded / bunkered into the one or more of the plurality of ballast tanks.

[0008] Optionally, the method further comprises distributing at least one of the lean solvent and the rich solvent among the plurality of ballast tanks based on the loading andthe stability of the offshore vessel. This may ensure that the loading and the stability of the offshore vessel remain in accordance with the acceptable loading and stability requirements, for example, during voyage of the offshore vessel. As the rich solvent is generated by the absorber, the rich solvent may need to be distributed among the plurality of ballast tanks to maintain the loading and the stability of the offshore vessel. Specifically, generation of the rich solvent from the lean solvent may increase a mass “M” of a particular volume of the lean solvent to a mass “M(1 +x)” of the particular volume of the rich solvent due to the absorbed carbon dioxide from the exhaust gas. As an example, the lean solvent may be taken from a port-side ballast tank located at distance “b” from a center of gravity of the offshore vessel. In case the same port-side ballast tank is used for replacing the lean solvent with the rich solvent, the resulting gravity moment will become M*x*b. To ensure the stability of the offshore vessel, the rich solvent may be distributed among two ballast tanks positioned opposite to the port-side ballast tank with respect to the center of gravity of the offshore vessel, such that each of the two ballast tanks contains the rich solvent having mass %*M*x. Then, the resulting gravity moment will become zero, thereby ensuring stability of the offshore vessel. In some implementations, the lean solvent may be pumped from a first pair of ballast tanks that are located opposite to a second pair of ballast tanks with respect to center of gravity of the offshore vessel, and the rich solvent may be returned with equal flow to the second pair of ballast tanks. Then, the stability may remain unchanged, although the loading is increased.

[0009] Optionally, the method further comprises offloading the rich solvent from one or more of the plurality of ballast tanks based on the loading and the stability of the offshore vessel. This may ensure that the loading and the stability of the offshore vessel remain in accordance with the acceptable loading and stability requirements of the offshore vessel, for example, when the rich solvent is offloaded / debunkered from the one or more of the plurality of ballast tanks.

[0010] Optionally, the method further comprises storing a supplementary liquid in at least one of the plurality of ballast tanks based on the loading and the stability of the offshore vessel. This may ensure that the loading and the stability of the offshore vessel remain in accordance with the acceptable loading and stability requirements of the offshore vessel, for example, in cases where distribution of the lean solvent and / or the rich solventamong the plurality of ballast tanks is not adequate to keep the offshore vessel in accordance with the acceptable loading and stability requirements.

[0011] According to a second aspect of the present invention, there is provided a system for removing carbon dioxide from an exhaust gas of an offshore vessel. The system comprises a plurality of ballast tanks. At least one ballast tank from the plurality of ballast tanks is for storing a lean solvent. The system further comprises an absorber configured to receive the exhaust gas containing carbon dioxide and the lean solvent for absorbing carbon dioxide from the exhaust gas, thereby generating a rich solvent containing the absorbed carbon dioxide. The system further comprises a feed conduit though which the lean solvent is flowable from the at least one ballast tank to the absorber. The system further comprises a discharge conduit though which the rich solvent is flowable from the absorber to at least one ballast tank from the plurality of ballast tanks.

[0012] The system may facilitate removing carbon dioxide from the exhaust gas while enabling better use of the plurality of ballast tanks. Specifically, the system may allow storing the lean solvent and the rich solvent in the plurality of ballast tanks, thereby obviating a need to allocate extra storage space in the offshore vessel for storing the lean solvent and the rich solvent. The system may further allow loading / bunkering a large volume of the lean solvent at once, which may allow the absorber to operate for a longer period of time during voyage of the offshore vessel. Also, the rich solvent and the lean solvent may replace ballast water that might otherwise be stored in the plurality of ballast tanks, thereby ensuring that the traditional functionality of the ballast tanks (e.g., to provide hydrostatic stability) is not compromised. The system may thus allow the offshore vessel to safely carry more cargo while reducing emissions from the offshore vessel.

[0013] Optionally, the discharge conduit is configurable to control the flow of the rich solvent from the absorber to one or more of the plurality of ballast tanks. Therefore, the discharge conduit may allow selectively storing the rich solvent in the one or more of the plurality of ballast tanks as per requirements.

[0014] Optionally, the system further comprises a distribution conduit arrangement for distributing at least one of the lean solvent and the rich solvent from one ballast tank from the plurality of ballast tanks to another ballast tank from the plurality of ballast tanks.The distribution conduit arrangement may fluidically connect the plurality of ballast tanks to each other, such that the at least one of the lean solvent and the rich solvent may be distributed among the plurality of ballast tanks. The distribution conduit arrangement may include a plurality of pipes and flow control components, such as valves, to control the flow of the lean solvent and / or the rich solvent among the plurality of ballast tanks.

[0015] Optionally, the system further comprises one or more sensors fluidically connectable between the absorber and one or more of the ballast tanks of the offshore vessel. The one or more sensors are configured to sense a density and a volume of the lean solvent and a density and a volume of the rich solvent. The system further comprises a processor communicably connectable to the one or more sensors. The processor is configured to determine a distribution plan for distributing at least one of the lean solvent and the rich solvent among the plurality of ballast tanks based on the density and the volume of the lean solvent and the density and the volume of the rich solvent. The processor may automatically determine the density and the volume of the lean solvent and the density and the volume of the rich solvent via the one or more sensors and generate the distribution plan, for example, on the basis of the loading and the stability of the offshore vessel, such that the loading and the stability remain in accordance with the acceptable loading and stability conditions.

[0016] Optionally, the system further comprises a distribution control module fluidically connectable to the distribution conduit arrangement and communicably connectable to the processor. The processor is configured to control the distribution control module to distribute the at least one of the rich solvent and the lean solvent among the plurality of ballast tanks based on the distribution plan. Therefore, the processor may control the distribution control module to automatically distribute the at least one of the rich solvent and the lean solvent among the plurality of ballast tanks based on the distribution plan.

[0017] According to a third aspect of the present invention, there is provided a hull assembly for an offshore vessel. The hull assembly comprises a hull and the system according to the second aspect. The absorber is disposed on the hull. The plurality of ballast tanks is located in the hull.

[0018] Features described herein in relation to one aspect of the present disclosure are explicitly disclosed in combination with the other aspects, to the extent that they are compatible.

[0019] Further features and advantages of the invention will become apparent from the following description of preferred embodiments of the invention, given by way of example only, which is made with reference to the accompanying drawings.BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

[0021] Figure 1 shows a schematic top view of an offshore vessel according to an example;

[0022] Figure 2 shows a schematic block diagram of a system for removing carbon dioxide from an exhaust gas of the offshore vessel according to an example; and

[0023] Figure 3 shows a schematic flow chart of a method of removing carbon dioxide from an exhaust gas of an offshore vessel according to an example.DETAILED DESCRIPTION

[0024] As used herein, the term “offshore” refers to a location within a body of water, e.g., a lake, a river, a sea, etc. The term “onshore” refers to an area of land in close proximity to the body of water.

[0025] As used herein, the term “offshore vessel” refers to a vehicle capable of travelling on water.

[0026] As used herein, the term “solvent” refers to a fluid that can absorb carbon dioxide from a gas containing carbon dioxide. Specifically, a solvent may react with the gas to absorb carbon dioxide from the gas. The absorbed carbon dioxide may remain boundwith the solvent until further processing (e.g., heating) of the solvent. Solvents useful in the present invention comprise solvents having a high carbon dioxide absorption capacity (e.g., greater than 2 moles CCh / kilogram). Examples of high carbon dioxide absorption capacity solvents comprise, but are not limited to, aminomethyl propanol (2- Amino-2-methylpropan-1-ol), methyldiethanolamine (2,2’-(Methylazanediyl)di(ethan-1- ol)) (MDEA), monoethanolamine (MEA), piperazine (1 ,4-Diazacyclohexane), tetraethylenepentamine (TEPA), and so forth.

[0027] As used herein, the term “lean solvent” refers to a solvent with a relatively low concentration of carbon dioxide. Lean solvents may be used to absorb carbon dioxide from a gas.

[0028] As used herein, the term “rich solvent” refers to a solvent with a relatively high concentration of carbon dioxide. Rich solvents can be generated by reacting lean solvents with a gas containing carbon dioxide, such that they become partly or fully saturated with carbon dioxide. The carbon dioxide contained in the rich solvent may be extracted by processing the rich solvent. When the carbon dioxide is extracted from the rich solvent, the rich solvent may return into a “lean solvent state.” In other words, the rich solvent may convert back to a lean solvent after extraction of the carbon dioxide therefrom. Consequently, after extraction of the carbon dioxide from the rich solvent, it may be reused for absorbing carbon dioxide from a gas.

[0029] As used herein, the term “ballast tank” refers to a container or a compartment of an offshore vessel that is typically used to provide hydrostatic stability to the offshore vessel and / or to ensure the structural integrity of the offshore vessel. Ballast tanks are structurally integral to an offshore vessel.

[0030] As used herein, the term “fluidically connectable” refers to two components between which a connection can be formed which allows a fluid to flow between the two components. The two components may be connected by one or more conduits or pipes to allow the flow of the fluid therebetween. Optionally, a pump, a valve, a regulator, or the like may be arranged between the two components to control the flow of the fluid between the two components.

[0031] As used herein, the term “communicably connectable” refers to direct connection between components and / or indirect connection between components via one or more intervening components. Such components and intervening components may include, but are not limited to, junctions, communication paths, components, circuit elements, circuits, functional blocks, and / or devices. As an example of indirect connection, a signal conveyed from a first component to a second component may be modified by one or more intervening components by modifying the form, nature, or format of information in a signal, while one or more elements of the information in the signal are nevertheless conveyed in a manner than can be recognized by the second component.

[0032] As used herein, the term “non-transitory storage medium” may represent one or more devices for storing data, including read only memory (ROM), programmable readonly memory (PROM), erasable programmable read-only memory (EPROM), random access memory (RAM), magnetic RAM, core memory, floppy disk, flexible disk, hard disk, magnetic tape, CD-ROM, flash memory devices, a memory card and / or other machine readable mediums for storing information. The term “machine-readable medium” includes, but is not limited to, portable or fixed storage devices, optical storage mediums, magnetic mediums, memory chips or cartridges, wireless channels, and various other mediums capable of storing, containing, or carrying instruction(s) and / or data. A machine-readable medium can be realized by virtualization, and can be a virtual machine readable medium including a virtual machine readable medium in a cloudbased instance.

[0033] As used herein, “at least one of A and B” should be understood to mean “only A, only B, or both A and B.”

[0034] Referring now to the figures, Figure 1 shows a schematic top view of an offshore vessel 10 according to an example. In this example, the offshore vessel 10 is a container ship. In other examples, the offshore vessel 10 may be another form of cargo vessel, such as a tanker, a dry-bulk carrier or a reefer ship, or a passenger vessel. In other examples, the offshore vessel 10 may be any other water-going vessel, such as a tugboat, or a recreational boat, such as a yacht.

[0035] The offshore vessel 10 comprises a hull assembly 12. The hull assembly 12 comprises a hull 14 and a system 100 for removing carbon dioxide from an exhaust gas 21 (schematically depicted by an arrow) of the offshore vessel 10. The exhaust gas 21 may be produced by a power plant (not shown) of the offshore vessel 10. The power plant may generate propulsion for moving the offshore vessel 10 in a body of water. Alternatively or additionally, the power plant may generate electricity for various equipment of the offshore vessel 10. In some examples, the power plant may comprise an internal combustion engine (such as a diesel engine).

[0036] The system 100 comprises a plurality of ballast tanks 120. The plurality of ballast tanks 120 are located in the hull 14. In this example, the plurality of ballast tanks 120 comprises a first ballast tank 120A, a second ballast tank 120B, a third ballast tank 120C, and a fourth ballast tank 120D. The first and third ballast tanks 120A, 120C are located at a bow (front end) of the hull 14. Further, the second and fourth ballast tanks 120B, 120D are located at a stern (rear end) of the hull 14. However, it may be noted that the plurality of ballast tanks 120 may include any number of ballast tanks 120 that may be disposed in any suitable arrangement. The number and the arrangement of the ballast tanks 120 may vary depending upon the offshore vessel 10.

[0037] At least one ballast tank 120 from the plurality of ballast tanks 120 is for storing a lean solvent 31 (schematically depicted by an arrow). In other words, the lean solvent 31 may be stored in at least one of the plurality of ballast tanks 120. For example, the lean solvent 31 may be stored in the first ballast tank 120A. In some examples, the lean solvent 31 may be stored in multiple ballast tanks 120 from the plurality of ballast tanks 120. For example, the lean solvent 31 may be stored in the first and fourth ballast tanks 120A, 120D.

[0038] In some examples, the lean solvent 31 may be stored into one or more of the plurality of ballast tanks 120 based on a loading and a stability of the offshore vessel 10. In other words, the lean solvent 31 may be bunkered into the one or more of the plurality of ballast tanks 120, such that the loading of the offshore vessel 10 remains under acceptable loading conditions and the stability of the offshore vessel 10 remains under acceptable stability conditions. For example, if a cargo load on the offshore vessel 10 is excessive at one portion of the hull 14, the lean solvent 31 may be stored into the ballasttanks 120 located at a corresponding opposite portion of the hull 14. In this way, the lean solvent 31 may be carried on the offshore vessel 10 without negatively affecting its loading and stability.

[0039] The system 100 further comprises an absorber 110. The absorber 110 is disposed on the hull 14. The absorber 110 is configured to receive the exhaust gas 21 containing carbon dioxide and the lean solvent 31 for absorbing carbon dioxide from the exhaust gas 21 , thereby generating a rich solvent 33 (schematically depicted by an arrow) containing the absorbed carbon dioxide.

[0040] The rich solvent 33 may be processed (for example, heated) to extract the absorbed carbon dioxide. Such a process of extracting the absorbed carbon dioxide may be referred to as “desorption.” The desorption may be performed offshore, e.g., on the offshore vessel 10 itself. Alternatively, the desorption may be performed onshore, e.g., in a desorption facility located on land. In such cases, the rich solvent 33 may be transported to the desorption facility by one or more transport vessels.

[0041] The absorber 110 may comprise a gas inlet 111 through which the absorber 110 receives the exhaust gas 21 , a gas outlet 112 through which the absorber 110 may discharge a carbon dioxide depleted gas 22 (schematically depicted by an arrow), a solvent inlet 113 through which the absorber 110 receives the lean solvent 31 , and a solvent outlet 114 through which the absorber 110 discharges the rich solvent 33. Optionally, the system 100 may further comprise a treatment module (not shown) for treating the exhaust gas 21 before the absorber 110 receives the exhaust gas 21 via the gas inlet 111. The treatment module may comprise, for example, a scrubber, a gas cooler, or both.

[0042] The system 100 further comprises a feed conduit 131 through which the lean solvent 31 is flowable from the at least one ballast tank 120 to the absorber 110. The feed conduit 131 may fluidically connect the at least one ballast tank 120 to the absorber 110 via the solvent inlet 113.

[0043] The system 100 further comprises a discharge conduit 133 through which the rich solvent 33 is flowable from the absorber 110 to at least one ballast tank 120 from theplurality of ballast tanks 120. The discharge conduit 133 may fluidically connect the at least one ballast tank 120 to the absorber 110 via the solvent outlet 114.

[0044] The discharge conduit 133 may be configurable to control the flow of the rich solvent 33 from the absorber 110 to one or more of the plurality of ballast tanks 120. Therefore, the discharge conduit 133 may allow selectively storing the rich solvent 33 in the one or more of the plurality of ballast tanks 120 as per requirements. It may be noted that the rich solvent 33 may be stored in the same ballast tank 120 from which the lean solvent 31 is received by the absorber 110 or in some other ballast tank 120 from the plurality of ballast tanks 120.

[0045] In this example, the system 100 further comprises a distribution conduit arrangement 140 (schematically depicted by a block) for distributing at least one of the lean solvent 31 and the rich solvent 33 from one ballast tank 120 from the plurality of ballast tanks 120 to another ballast tank 120 from the plurality of ballast tanks 120. The distribution conduit arrangement 140 may include a plurality of conduits (not shown) that can fluidically connect the plurality of ballast tanks 120 to each other. For example, the distribution conduit arrangement 140 may include a network of pipes. The plurality of conduits of the distribution conduit arrangement 140 may be arranged in a way that allows distribution of the lean solvent 31 and / or the rich solvent 33 among the plurality of ballast tanks 120.

[0046] Further, in this example, the feed conduit 131 and the discharge conduit 133 fluidically connect the absorber 110 to the plurality of ballast tanks 120 via the distribution conduit arrangement 140. However, in some other examples, the distribution conduit arrangement 140 may be different from a conduit system (not shown) that can fluidically connect the plurality of ballast tanks 120 to the absorber 110. In such examples, the distribution conduit arrangement 140 may be solely used for distributing the at least one of the lean solvent 31 and the rich solvent 33 among the plurality of ballast tanks 120 and the conduit system may be used for providing the absorber 110 with the lean solvent 31 from one or more of the plurality of ballast tanks 120 and storing the rich solvent 33 generated by the absorber 110 in one or more of the plurality of ballast tanks 120.

[0047] In this example, the system 100 further comprises flow control components 142, such as valves, filters, pumps, and / or other components, fluidically connected to the distribution conduit arrangement 140 for controlling a flow of the lean solvent 31 and / or the rich solvent 33 among the plurality of ballast tanks 120 and / or to and from the absorber 110. The flow control components 142 may be operable manually and / or automatically.

[0048] The lean solvent 31 and / or the rich solvent 33 may be distributed among the plurality of ballast tanks 120 to redistribute a weight of the offshore vessel 10 and control an attitude (or draught) of the offshore vessel 10. This may be to correct, or set, a trim of the offshore vessel 10, such as during a voyage, or during a loading and / or unloading of cargo during a port stay.

[0049] In this way, the lean solvent 31 and / or the rich solvent 33 may be distributed among the plurality of ballast tanks 120 to control the stability of, such as to change the attitude of, the offshore vessel 10. The system 100 may also be used to control a pitch and / or a heel of the offshore vessel 10.

[0050] Further, as the rich solvent 33 contains the absorbed carbon dioxide, a density of the rich solvent 33 may be different than a density of the lean solvent 31. Specifically, the density of the rich solvent 33 may be greater than the density of the lean solvent 31. In some examples, the density of the rich solvent 33 may be greater than the density of the lean solvent 31 by a factor of at least 1.1 , at least 1 .2, at least 1.3, or at least 1 .4. As the lean solvent 31 and the rich solvent 33 may have different densities, their densities may be important factors to consider while storing them in the plurality of ballast tanks 120. Therefore, distribution of the lean solvent 31 and / or the rich solvent 33 among the plurality of ballast tanks 120 may be based on the respective densities of the lean solvent 31 and / or the rich solvent 33. In certain implementations, the density of the lean solvent 31 and the density of the rich solvent 33 may be determined based on the absorption characteristics of the specific solvent used. For example, the density of the rich solvent 33 may be determined from an experimental setup.

[0051] The density of the rich solvent 33 being greater than the density of the lean solvent 31 may enable layering of the rich solvent 33 and the lean solvent 31 in the sameballast tank 120. Specifically, the rich solvent 33 (having higher density than the lean solvent 31) may sink to a bottom of the ballast tank 120. Baffle plates may be added to the ballast tank 120 in order to efficiently separate the lean solvent 31 from the rich solvent 33 in the ballast tank 120. Further, the lean solvent 31 may be extracted from one end and the rich solvent 33 to be returned to an opposite end of a single ballast tank 120 or multiple connected ballast tanks 120.

[0052] In some cases, it may be desired to offload the rich solvent 33 from one or more of the plurality of ballast tanks 120, for example, to extract the absorbed carbon dioxide from the rich solvent 33. In such cases, the rich solvent 33 may be offloaded from the one or more of the plurality of ballast tanks 120 based on the loading and the stability of the offshore vessel 10. In this way, the offshore vessel 10 may remain under acceptable loading and stability conditions during offloading of the rich solvent 33.

[0053] In some cases, distribution of the lean solvent 31 and / or the rich solvent 33 among the plurality of ballast tanks 120 may not be adequate to keep the offshore vessel in accordance with the acceptable loading and stability requirements. Thus, in this example, the system 100 further comprises a supplementary liquid loading device 135 configured to load a supplementary liquid 35 (schematically depicted by an arrow) into one or more of the plurality of ballast tanks 120. The supplementary liquid loading device 135 may include, for example, a motor, a pump, a conduit, and so forth.

[0054] In this example, the supplementary liquid loading device 135 is fluidically coupled to the plurality of ballast tanks 120 via the distribution conduit arrangement 140. However, in other examples, the supplementary liquid loading device 135 may be fluidically couplable to the plurality of ballast tanks 120 via a conduit system (not shown) different from the distribution conduit arrangement 140. The supplementary liquid loading device 135 may be used to load the supplementary liquid 35 into one or more of the plurality of ballast tanks 120 to control the stability of, or to change the attitude, of the offshore vessel 10, if required. The supplementary liquid 35 may be, for example, water on which the offshore vessel 10 travels.

[0055] Therefore, the system 100 may facilitate removing carbon dioxide from the exhaust gas 21 while enabling better use of the plurality of ballast tanks 120. Specifically,the system 100 may allow storing the lean solvent 31 and the rich solvent 33 in the plurality of ballast tanks 120, thereby obviating a need to allocate extra storage space in the offshore vessel 10 for storing the lean solvent 31 and the rich solvent 33. The system 100 may further allow loading / bunkering a large volume of the lean solvent 31 at once, which may allow the absorber 110 to operate for a longer period of time during voyage of the offshore vessel 10. Also, the rich solvent 33 and the lean solvent 31 may replace ballast water that might otherwise be stored in the plurality of ballast tanks 120, thereby ensuring that the traditional functionality of the ballast tanks 120 (e.g., to provide hydrostatic stability and / or load distribution within the allowable strength limits of the hull 14) is not compromised. The system 100 may thus allow the offshore vessel 10 to safely carry more cargo while reducing emissions from the offshore vessel 10.

[0056] Figure 2 shows a schematic block diagram of the system 100 according to another example. Some elements of the system 100 that are shown in Figure 1 are not shown in Figure 2 for illustrative purposes.

[0057] In this example, the system 100 further comprises one or more sensors 121 fluidically connectable between the absorber 110 and one or more of the ballast tanks 120 of the offshore vessel 10. The one or more sensors 121 are configured to sense the density and a volume-flow of the lean solvent 31 and the density and a volume-flow of the rich solvent 33. The one or more sensors 121 may include, for example, flow rate sensors, density sensors, and so forth. For example, the volume of the lean solvent 31 and the volume of the rich solvent 33 may be determined based on rate of flow of the lean and rich solvents 31 , 33 in a time period.

[0058] Specifically, in this example, the one or more sensors 121 comprises a first sensor 121 A corresponding to the first ballast tank 120A, a second sensor 121 B corresponding to the second ballast tank 120B, a third sensor 121 C corresponding to the third ballast tank 120C, and a fourth sensor 121 D corresponding to the fourth ballast tank 120D.

[0059] In this example, the system 100 further comprises a processor 150 communicably connectable to the one or more sensors 121. Moreover, in this example,the system 100 further comprises a non-transitory storage medium 160 communicably connectable to the processor 150.

[0060] The processor 150 is configured to determine a distribution plan 155 for distributing at least one of the lean solvent 31 and the rich solvent 33 among the plurality of ballast tanks 120 based on the density and the volume of the lean solvent 31 and the density and the volume of the rich solvent 33. The processor 150 may store the distribution plan 155 on the non-transitory storage medium 160. In some examples, the processor 150 may output the distribution plan 155 to a user via an output device (e.g., a monitor).

[0061] The processor 150 may automatically determine the density and the volume of the lean solvent 31 and the density and the volume of the rich solvent 33 via the one or more sensors 121 and generate the distribution plan 155 on the basis of the loading and the stability of the offshore vessel 10 (shown in Figure 1), such that the loading and the stability remain in accordance with the acceptable loading and stability conditions.

[0062] In this example, the system 100 further comprises a distribution control module 145 fluidically connectable to the distribution conduit arrangement 140. The distribution control module 145 is communicably connectable to the processor 150. The processor 150 is configured to control the distribution control module 145 to distribute the at least one of the rich solvent 33 and the lean solvent 31 among the plurality of ballast tanks 120 based on the distribution plan 155. Thus, the processor 150 may autonomously distribute the lean solvent 31 and / or the rich solvent 33 by controlling the distribution control module 145 based on the distribution plan 155. In some examples, the distribution control module 145 may control the flow control components 142 (shown in Figure 1). In some examples, the distribution control module 145 may comprise the flow control components 142. The distribution control module 145 may, for example, hydraulically or pneumatically control the flow control components 142.

[0063] Figure 3 shows a method 200 for removing carbon dioxide from an exhaust gas of an offshore vessel having a plurality of ballast tanks according to an example. In this example, the method 200 can be performed using the system 100 depicted in Figures 1 and 2.

[0064] The method 200 comprises storing 210 a lean solvent in at least one ballast tank from the plurality of ballast tanks. For example, the method 200 may comprise storing 210 the lean solvent 31 in at least one ballast tank 120 from the plurality of ballast tanks 120.

[0065] The method 200 further comprises receiving 220, at an absorber, the lean solvent and the exhaust gas containing carbon dioxide. For example, the method 200 may comprise receiving 220, at the absorber 110, the lean solvent 31 and the exhaust gas 21 containing carbon dioxide.

[0066] The method 200 further comprises absorbing 230, via the lean solvent received by the absorber, carbon dioxide from the exhaust gas to generate a rich solvent containing the absorbed carbon dioxide. For example, the method 200 may comprise absorbing 230, via the lean solvent 31 received by the absorber 110, carbon dioxide from the exhaust gas 21 to generate the rich solvent 33 containing the absorbed carbon dioxide.

[0067] The method 200 further comprises storing 240 the rich solvent generated by the absorber in at least one ballast tank from the plurality of ballast tanks. For example, the method 200 may comprise storing 240 the rich solvent 33 generated by the absorber 110 in at least one ballast tank 120 from the plurality of ballast tanks 120. It may be noted that the rich solvent 33 may be stored in the same ballast tank 120 from which the lean solvent 31 is received by the absorber 110 or in some other ballast tank 120 from the plurality of ballast tanks 120.

[0068] The method 200 may facilitate removing carbon dioxide from the exhaust gas while enabling better use of the plurality of ballast tanks of the offshore vessel. Specifically, storing the lean solvent and the rich solvent in the plurality of ballast tanks may obviate a need to allocate extra storage space in the offshore vessel for storing the lean solvent and the rich solvent. It may further allow loading / bunkering a large volume of the lean solvent at once, which may allow the absorber to operate for a longer period of time during voyage of the offshore vessel. Further, the rich solvent and the lean solvent may be used in place of ballast water to ensure that the traditional functionality of the ballast tanks (e.g., to provide hydrostatic stability and / or load distribution) is notcompromised. The method may thus allow the offshore vessel to safely carry more cargo while reducing emissions from the offshore vessel.

[0069] In this example, the method 200 further comprises storing 250 at least one of the lean solvent and the rich solvent among the plurality of ballast tanks based on a density of the lean solvent and / or a density of the rich solvent. For example, the method 200 may comprise storing 250 at least one of the lean solvent 31 and the rich solvent 33 among the plurality of ballast tanks 120 based on the density of the lean solvent 31 and / or the density of the rich solvent 33.

[0070] As the lean solvent and the rich solvent may have different densities, their densities may be important factors to consider while storing them in the plurality of ballast tanks. Therefore, distribution of the lean solvent and / or the rich solvent among the plurality of ballast tanks may be based on the respective densities of the lean solvent and / or the rich solvent.

[0071] In this example, the method 200 further comprises storing 260 the lean solvent into one or more of the plurality of ballast tanks based on a loading and a stability of the offshore vessel. For example, the method 200 may comprise storing 260 the lean solvent 31 into one or more of the plurality of ballast tanks 120 based on the loading and the stability of the offshore vessel 10. In other words, the bunkering of the lean solvent 31 on the offshore vessel 10 may be based on the loading and the stability of the offshore vessel 10.

[0072] In this example, the method 200 further comprises distributing 270 at least one of the lean solvent and the rich solvent among the plurality of ballast tanks based on the loading and the stability of the offshore vessel. For example, the method 200 may comprise distributing 270 at least one of the lean solvent 31 and the rich solvent 33 among the plurality of ballast tanks 120 based on the loading and the stability of the offshore vessel 10.

[0073] In this example, the method 200 further comprises offloading 280 the rich solvent from one or more of the plurality of ballast tanks based on the loading and the stability of the offshore vessel. For example, the method 200 may comprise offloading 280 the richsolvent 33 from one or more of the plurality of ballast tanks 120 based on the loading and the stability of the offshore vessel 10. In other words, the de-bunkering of the rich solvent 33 from the offshore vessel 10 may be based on the loading and the stability of the offshore vessel 10.

[0074] In this example, the method 200 further comprises storing 290 a supplementary liquid in at least one of the plurality of ballast tanks based on the loading and the stability of the offshore vessel. For example, the method 200 may further comprise storing 290 the supplementary liquid 35 in at least one of the plurality of ballast tanks 120 based on the loading and the stability of the offshore vessel 10. The supplementary liquid 35 may be stored in the at least one of the plurality of ballast tanks 120, for example, in cases where distribution of the lean solvent 31 and / or the rich solvent 33 among the plurality of ballast tanks 120 is not adequate to keep the offshore vessel 10 in accordance with the acceptable loading and stability requirements

[0075] Embodiments of systems and methods of the disclosure are set out in the following items:

[0076] Item 1 . A method of removing carbon dioxide from an exhaust gas of an offshore vessel having a plurality of ballast tanks, the method comprising: storing a lean solvent in at least one ballast tank from the plurality of ballast tanks; receiving, at an absorber, the lean solvent and the exhaust gas containing carbon dioxide; absorbing, via the lean solvent received by the absorber, carbon dioxide from the exhaust gas to generate a rich solvent containing the absorbed carbon dioxide; and storing the rich solvent generated by the absorber in at least one ballast tank from the plurality of ballast tanks.

[0077] Item 2. The method according to item 1 , further comprising storing at least one of the lean solvent and the rich solvent among the plurality of ballast tanks based on a density of the lean solvent and / or a density of the rich solvent.

[0078] Item 3. The method according to item 1 or 2, further comprising storing the lean solvent into one or more of the plurality of ballast tanks based on a loading and a stability of the offshore vessel.

[0079] Item 4. The method according to any one of the items 1 to 3, further comprising distributing at least one of the lean solvent and the rich solvent among the plurality of ballast tanks based on the loading and the stability of the offshore vessel.

[0080] Item 5. The method according to any one of the items 1 to 4, further comprising offloading the rich solvent from one or more of the plurality of ballast tanks based on the loading and the stability of the offshore vessel.

[0081] Item 6. The method according to any one of the items 1 to 5, further comprising storing a supplementary liquid in at least one of the plurality of ballast tanks based on the loading and the stability of the offshore vessel.

[0082] Item 7. A system for removing carbon dioxide from an exhaust gas of an offshore vessel, the system comprising: a plurality of ballast tanks, wherein at least one ballast tank from the plurality of ballast tanks is for storing a lean solvent; an absorber configured to receive the exhaust gas containing carbon dioxide and the lean solvent for absorbing carbon dioxide from the exhaust gas, thereby generating a rich solvent containing the absorbed carbon dioxide; a feed conduit through which the lean solvent is flowable from the at least one ballast tank to the absorber; and a discharge conduit through which the rich solvent is flowable from the absorber to at least one ballast tank from the plurality of ballast tanks.

[0083] Item 8. The system according to item 7, wherein the discharge conduit is configurable to control the flow of the rich solvent from the absorber to one or more of the plurality of ballast tanks.

[0084] Item 9. The system according to item 7 or 8, further comprising a distribution conduit arrangement for distributing at least one of the lean solvent and the rich solventfrom one ballast tank from the plurality of ballast tanks to another ballast tank from the plurality of ballast tanks.

[0085] Item 10. The system according to item 9, further comprising: one or more sensors fluidically connectable between the absorber and one or more of the ballast tanks of the offshore vessel, wherein the one or more sensors are configured to sense a density and a volume of the lean solvent and a density and a volume of the rich solvent; and a processor communicably connectable to the one or more sensors, wherein the processor is configured to determine a distribution plan for distributing at least one of the lean solvent and the rich solvent among the plurality of ballast tanks based on the density and the volume of the lean solvent and the density and the volume of the rich solvent.

[0086] Item 11 . The system according to item 10, further comprising a distribution control module fluidically connectable to the distribution conduit arrangement and communicably connectable to the processor, wherein the processor is configured to control the distribution control module to distribute the at least one of the rich solvent and the lean solvent among the plurality of ballast tanks based on the distribution plan.

[0087] Item 12. A hull assembly for an offshore vessel, the hull assembly comprising a hull and the system according to any one of the items 7 to 11 , wherein the absorber is disposed on the hull, and wherein the plurality of ballast tanks is located in the hull.

[0088] In other embodiments, two or more of the above described embodiments may be combined. In other embodiments, features of one embodiment may be combined with features of one or more other embodiments.

[0089] Example embodiments of the present invention have been discussed, with particular reference to the examples illustrated. However, it will be appreciated that variations and modifications may be made without departing from the scope of the invention as defined by the appended claims.

Claims

CLAIMS1 . A method of removing carbon dioxide from an exhaust gas of an offshore vessel having a plurality of ballast tanks, the method comprising: storing a lean solvent in at least one ballast tank from the plurality of ballast tanks; receiving, at an absorber, the lean solvent and the exhaust gas containing carbon dioxide; absorbing, via the lean solvent received by the absorber, carbon dioxide from the exhaust gas to generate a rich solvent containing the absorbed carbon dioxide; and storing the rich solvent generated by the absorber in at least one ballast tank from the plurality of ballast tanks.

2. The method according to claim 1 , further comprising storing at least one of the lean solvent and the rich solvent among the plurality of ballast tanks based on a density of the lean solvent and / or a density of the rich solvent.

3. The method according to claim 1 or 2, further comprising storing the lean solvent into one or more of the plurality of ballast tanks based on a loading and a stability of the offshore vessel.

4. The method according to any one of the claims 1 to 3, further comprising distributing at least one of the lean solvent and the rich solvent among the plurality of ballast tanks based on the loading and the stability of the offshore vessel.

5. The method according to any one of the claims 1 to 4, further comprising offloading the rich solvent from one or more of the plurality of ballast tanks based on the loading and the stability of the offshore vessel.

6. The method according to any one of the claims 1 to 5, further comprising storing a supplementary liquid in at least one of the plurality of ballast tanks based on the loading and the stability of the offshore vessel.

7. A system for removing carbon dioxide from an exhaust gas of an offshore vessel, the system comprising:a plurality of ballast tanks, wherein at least one ballast tank from the plurality of ballast tanks is for storing a lean solvent; an absorber configured to receive the exhaust gas containing carbon dioxide and the lean solvent for absorbing carbon dioxide from the exhaust gas, thereby generating a rich solvent containing the absorbed carbon dioxide; a feed conduit through which the lean solvent is flowable from the at least one ballast tank to the absorber; and a discharge conduit through which the rich solvent is flowable from the absorber to at least one ballast tank from the plurality of ballast tanks.

8. The system according to claim 7, wherein the discharge conduit is configurable to control the flow of the rich solvent from the absorber to one or more of the plurality of ballast tanks.

9. The system according to claim 7 or 8, further comprising a distribution conduit arrangement for distributing at least one of the lean solvent and the rich solvent from one ballast tank from the plurality of ballast tanks to another ballast tank from the plurality of ballast tanks.

10. The system according to claim 9, further comprising: one or more sensors fluidically connectable between the absorber and one or more of the ballast tanks of the offshore vessel, wherein the one or more sensors are configured to sense a density and a volume of the lean solvent and a density and a volume of the rich solvent; and a processor communicably connectable to the one or more sensors, wherein the processor is configured to determine a distribution plan for distributing at least one of the lean solvent and the rich solvent among the plurality of ballast tanks based on the density and the volume of the lean solvent and the density and the volume of the rich solvent.

11. The system according to claim 10, further comprising a distribution control module fluidically connectable to the distribution conduit arrangement and communicably connectable to the processor, wherein the processor is configured to control the distribution control module to distribute the at least one of the rich solvent and the lean solvent among the plurality of ballast tanks based on the distribution plan.

12. A hull assembly for an offshore vessel, the hull assembly comprising a hull and the system according to any one of the claims 7 to 11 , wherein the absorber is disposed on the hull, and wherein the plurality of ballast tanks is located in the hull.

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