NOVEL CO2 MARITIME TRANSSHIPMENT AND STORAGE SYSTEM

Abstract

 A COz maritime transshipment and storage system, consisting of five parts, namely CO₂ transmission, CO₂ loading and unloading, CO₂ transportation, CO₂ injection, and CO₂ storage. When dock loading conditions are satisfied, a CO₂ land storage terminal (3) conveys to a CO₂ filling apparatus by means of a land pipeline (5), a CO₂ transportation ship is filled, and after a destination is reached, dock unloading is performed by means of a CO₂ transshipment system (22), and transmission to a CO₂ injection module (23) is performed by means of a pipeline, for injection to a land or seabed CO₂ storage site for storage. When dock loading conditions are not satisfied, the CO₂ land storage terminal (3) conveys to a CO₂ maritime floating storage apparatus by means of a pipeline, the CO₂ transportation ship moors with said apparatus in an adjacent or side-by-side mode, CO₂ filling is completed by means of soft pipe transmission, and after the CO₂ transportation ship reaches a target sea area, transmission to a CO₂ maritime injection platform is performed by means of an internal turret apparatus, a seabed pipeline (6) and an underwater vertical pipe (13), for injection by means of a seabed wellhead (26) to a seabed CO₂ storage site (25) for storage.

Description

[0001] The disclosure relates to the field of carbon capture, transportation, and storage (CCUS), and more specifically, to a novel CO₂ maritime transshipment and storage system for the separation of CO₂ from sources such as industrial processes, energy utilization, or the atmosphere. The separated CO₂ is then transported and stored in geological formations, on land or under the sea, with the objective of achieving permanent reduction of CO₂ levels in the atmosphere.

[0002] Under the objective of achieving carbon neutrality, the aggressive advantage of the CCUS technology represents a strategic decision for China to significantly reduce carbon dioxide (CO₂) emissions while safeguarding future energy security. The CCUS technology is also pivotal for fostering ecological civilization and facilitating sustainable development. Unlike the development of new alternative energy sources, CCUS technology effectively reduces greenhouse gas emissions in the short term. Developing CCUS technology helps to balance the ongoing reliance on fossil fuels with the implementation of carbon reduction policies. Additionally, CCUS is a key technical method for maintaining the flexibility of power systems within the framework of carbon neutrality. Moreover, the CCUS technology offers viable pathways for achieving zero emissions in energy-intensive industries, thereby enhancing China's influence in the international low-carbon discourse.

[0003] China has prioritized the development of CCUS technology, making significant strides in onshore research and application. However, compared to other countries, China initiated research on marine CO₂ storage later than other countries, leaving areas such as CO₂ ocean transportation and seabed storage largely unexplored. Marine carbon sequestration offers potential advantages over onshore methods, including being located far from residential areas, which enhances its reliability and environmental compatibility. China's main carbon emission sources are concentrated in coastal areas, where nearby coastal basins offer favourable conditions for carbon sequestration. Additionally, China possesses robust design and manufacturing capabilities in the marine and shipbuilding sectors, providing favourable conditions for the implement of ocean CCUS. Although the cost of marine carbon sequestration is slightly higher than that of onshore alternatives, the flexibility afforded by maritime transportation allows for the serving of a broader range of carbon sources. Furthermore, as domestic carbon tax policies and carbon trading markets evolve, the economic feasibility of ocean CCUS is expected to improve.

[0004] To solve the aforesaid problems, the first objective of the disclosure is to provide a novel CO₂ maritime transshipment and storage system to enhance the efficiency of CO₂ transportation. The novel CO₂ maritime transshipment and storage system facilitate the effective CO₂ storage and supports the growth of the carbon trading market, thereby creating significant economic value.

[0005] The novel CO₂ maritime transshipment and storage system comprises a CO₂ transmission part, a CO₂ loading and unloading part, a CO₂ transportation part, a CO₂ injection part, and a CO₂ storage part.

[0006] In a class of this embodiment, when loading conditions are satisfied, liquid CO₂ is transported from an onshore CO₂ storage terminal to a CO₂ loading device through an onshore pipeline; the CO₂ is then transferred to a CO2 transport ship; when the CO₂ transport ship reaches a designated sea area, the liquid CO₂ is offloaded via a CO₂ transfer system, conveyed to a CO₂ injection module through the onshore pipeline, and then is injected into an onshore CO₂ storage site or a submarine CO₂ storage site.

[0007] In a class of this embodiment, when the loading conditions are not satisfied, the liquid CO₂ is transported from the onshore CO₂ storage terminal to a floating CO₂ storage device through a subsea pipeline; the CO₂ transport ship is moored in an inline or side-by-side configuration with the floating CO₂ storage device; the CO₂ is offloaded from the CO₂ transport ship to the floating CO₂ storage device via a hose; upon reaching the designated sea area, the CO₂ transport ship is moored in an inline or side-by-side configuration with the floating CO₂ storage device; the floating CO₂ storage device comprises a plurality of internal turrets; the CO₂ is transferred from the CO₂ transport ship to the floating CO₂ storage device through the hose; subsequently, the CO₂ is transmitted to an offshore CO₂ injection platform through the plurality of internal turrets, a subsea pipeline, and an underwater riser; finally, the CO₂ is injected into a submarine CO₂ storage site through a submarine wellhead, ensuring long-term storage.

[0008] When the loading conditions are not satisfied, the CO₂ is transmitted from the onshore CO₂ storage terminal to the floating CO₂ storage device through the subsea pipeline; after the floating CO₂ storage device arrives at the designated sea area, the CO₂ is conveyed to the offshore CO₂ injection platform through the plurality of internal turrets, the subsea pipeline, and the underwater riser; finally, the CO₂ is injected into the submarine CO₂ storage site through a submarine wellhead, ensuring long-term storage.

[0009] The onshore pipeline, the subsea pipeline, the underwater riser, and the hose are a set of pipelines having thermal insulation and pressure-assistant properties. The CO₂ transmitted through the set of pipelines is in gaseous, liquid, or supercritical state.

[0010] When the CO₂ is in a liquid state, the pressure within the set of pipelines ranges from 0.4 MPa to 7.39 MPa. When the CO₂ is in a supercritical state, the CO₂ in the set of pipelines is maintained at temperatures above 31.3°C, with the pressure exceeding 7.39 MPa. When the CO₂ is in a gaseous state, the pressure within the set of pipelines ranges from 0 to 7.39 MPa.

[0011] The CO₂ transport ship comprises a C-type tank for storage; the CO₂ transport ship is used to contain the CO₂ at pressures ranging from 0.4 MPa to 2.1 MPa.

[0012] The novel CO₂ maritime transshipment and storage system is applicable to the maritime transshipment and storage of CO₂ under various conditions. The novel CO₂ maritime transshipment and storage system optimized the efficiency of CO₂ transportation. The optimization establishes a foundation for CO₂ storage operations and facilitates the growth of the carbon trading market, thereby creating significant economic value.

[0013] The second objective of the disclosure is to provide a deep-sea storage method that is cost-effective, efficient, and allows for repeated use of a liquid CO₂ tank. The deep-sea storage method comprises:

S1. injecting liquid CO₂ into a liquid CO₂ tank; where, the liquid CO₂ tank comprises a tank body used to store the liquid CO₂; the tank body comprises a thermal insulation layer; the liquid CO₂ tank further comprises a discharge tank and an injection device; the discharge tank and the injection device are disposed on a first end and a second end of the tank body, respectively; the injection device comprises a unidirectional valve; the center of gravity of the tank body is tilted towards the first end of the tank body; the liquid CO₂ tank further comprises a nitrogen generation device disposed inside the tank body, specifically disposed at the second end of the tank body; the discharge device comprises a pressure-controlled relief device; and the liquid CO₂ tank further comprises a pressure-controlled valve;

S2. transporting, by a ship, the liquid CO₂ tank to an ocean storage area;

S3. releasing the liquid CO₂ tank into the seawater; where, the center of gravity of the tank body is tilted towards the first end of the tank body; the liquid CO₂ tank sinks in a vertical position, with the first end of the tank body facing downward;

S4. opening the pressure-controlled relief device to release the internal pressure when the internal pressure reaches the activation pressure of the pressure-controlled relief device;

S5. opening the injection device to permit the seawater to flow into the liquid CO₂ tank when the external seawater pressure reaches the activation pressure of the injection device;

S6. fully opening both the injection device and the discharge device when the liquid CO₂ tank reaches a designated CO₂ storage depth, and closing the injection device when the liquid CO₂ tank is filled with the seawater; where, the injection device and the discharge device are actuated to an open state, permitting the release of the liquid CO₂ from the liquid CO₂ tank;

S7. activating the nitrogen generation device to produce nitrogen gas, and closing the discharge device to seal the liquid CO₂ tank after the seawater exit the liquid CO₂ tank; where, the nitrogen gas displaces the seawater from the liquid CO₂ tank, making the liquid CO₂ tank buoyant and causing the liquid CO₂ tank to float on the surface of the sea; and

S8. retrieving the liquid CO₂ tank floating on the surface of the sea due to buoyancy.

[0014] In a class of this embodiment, the liquid CO₂ tank achieves a center of gravity that is biased towards the first end of the tank body by attaching a fixed weight.

[0015] In a class of this embodiment, the liquid CO₂ tank further comprises a satellite positioning device used to locate the liquid CO₂ tank when the liquid CO₂ tank floats to the surface of the sea due to buoyancy.

[0016] In a class of this embodiment, the liquid CO₂ tank further comprises a position monitoring device used to determine the depth at which the liquid CO₂ tank has sunk; each of the injection device and the discharge device has a remote control mechanism; the remote control mechanisms allow the injection device and the discharge device to operate respectively when the liquid CO₂ tank sinks to a target depth as detected by the position monitoring device.

[0017] In a class of this embodiment, the liquid CO₂ tank has a maximum allowable pressure of 30 bar, and in S6, a minimum depth for CO₂ storage is 1000 meters underwater.

[0018] The disclosure addresses the challenge of safely transporting and storing CO₂ in deep-sea environments while keeping costs low. Specifically, the disclosure provides the liquid CO₂ tank that is capable of being repeatedly recovered and reused after releasing the liquid CO₂. The liquid CO₂ tank uses pressure control to automatically discharge the liquid CO₂ at the target depth. Compared to the related art, the pressure control technology makes the operation safer and more reliable by minimizing the need for manual control. Additionally, the liquid CO₂ tank is able to suspend in the seawater, releasing the liquid CO₂ while floating rather than resting on the seabed. The suspend design allows the liquid CO₂ tank to be reused for further operations.

FIG. 1 is a schematic diagram of a general layout of CO₂ onshore storage according to one example of the disclosure;

FIG. 2 is a schematic diagram of a general layout of CO₂ seabed storage according to one example of the disclosure;

FIG. 3 is a flowchart of a first part of a novel CO₂ maritime transshipment and storage system according to one example of the disclosure;

FIG. 4 is a flowchart of a second part of a novel CO₂ maritime transshipment and storage system according to one example of the disclosure;

FIG. 5 is a flowchart of a third part of a novel CO₂ maritime transshipment and storage system according to one example of the disclosure;

FIG. 6 is a flowchart of a fourth part of a novel CO₂ maritime transshipment and storage system according to one example of the disclosure;

FIG. 7 is a schematic diagram of a liquid CO₂ tank according to one example of the disclosure;

FIG. 8 is a schematic diagram of a part of a discharge device shown in FIG. 7;

FIG. 9 is a schematic diagram of a state of a liquid CO₂ tank transported by a ship according to one example of the disclosure;

FIG. 10 is a process of achieving CO₂ storage in a target sea area;

FIG. 11 is a schematic diagram showing a state after a liquid CO₂ tank has released liquid CO₂ according to one example of the disclosure;

FIG. 12 is a schematic diagram showing a process of the liquid CO₂ tank returning;

FIG. 13 is a schematic diagram showing a state of the liquid CO₂ tank being recovered;

FIG. 14 is a schematic diagram showing a state of a ship completing the recovery of the liquid CO₂ tank.

[0019] In the drawings, the following reference numbers are used:
1. Industrial activities; 2. CO₂ capture module; 3. Onshore CO₂ storage terminal; 4. Onshore CO₂ loading arm; 5. Onshore CO₂ transmission pipeline; 6. Subsea CO₂ transmission pipeline; 7. First CO₂ transport ship; 8. Second CO₂ transport ship; 9. First floating CO₂ storage device; 10. Third CO₂ transport ships; 11. Catenary anchor leg mooring device; 12. Floating hose; 13. Underwater riser; 14. Mooring line; 15. Mooring anchor chain; 16. Soft-rigid arm anchor leg mooring device; 17. Transmission hose; 18. Second floating CO₂ storage device; 19. Jacket-type CO₂ pressurized transmission platform; 20.COz booster transmission module; 21.COz loading and unloading dock; 22.CO₂ transfer system; 23.First CO₂ injection module; 24.Onshore CO₂ storage site. 25. Submarine CO₂ storage site; 26. Submarine wellhead; 27. Conduit-type CO₂ injection platform; 28.Second CO₂ injection module; 91.lnjection device; 92.Discharge device; 93.Satellite positioning device; 94.Nitrogen generation device; 95.Tank body; 96. Pressure-controlled relief device; and 97.Gas escape device.

[0020] FIG. 1 is a schematic diagram of a general layout of CO₂ onshore storage. In the process of managing CO₂ emissions from industrial activities, CO₂ produced 1 is collected by a CO₂ capture module 2 and then stored in liquid form at an onshore CO₂ storage terminal 3. The liquid CO₂ is transported over a long distance to a submarine wellhead for storage. Specifically, when a CO₂ transport ship is docked, the liquid CO₂ is transported to an onshore CO₂ loading arm 4 via an onshore CO₂ transportation pipeline 5 and then is offloaded to a first CO₂ transport ship 7. Alternatively, the liquid CO₂ is transferred to a catenary anchor leg mooring device 11 via a subsea CO₂ transmission pipeline 6 and an underwater riser 13, and then is offloaded to the first CO₂ transport ship 7 through a floating hose 12. Alternatively, the liquid CO₂ is transferred to a soft-rigid arm anchor leg mooring device 16 through the subsea CO₂ transport pipeline 6 and the underwater riser 13, and then offloaded to the first CO₂ transport ship 7 through a transmission hose 17.

[0021] A first floating CO₂ storage device 9 comprises a plurality of internal turrets disposed in the nearshore waters to improve the efficiency of CO₂ storage and transmission. The CO₂ from the industrial activities 1 is collected by the CO₂ capture module 2, and then transmitted in liquid form through the subsea CO₂ transmission pipeline 6 to the first floating CO₂ storage device 9. The first floating CO₂ storage device 9 is used to transfer the CO₂ to a second mooring CO₂ transport ship 8 and a third CO₂ transport ship 10. The term "The second CO₂ transport ship", as used herein, refers to a CO₂ transport ship that is moored in an inline configuration with the first floating CO₂ storage device 9 or a second floating CO₂ storage device 18. The term "third CO₂ transport ship", as used herein, refers to a CO₂ transport ship that is moored in a side-by-side configuration with the first floating CO₂ storage device 9 or a second floating CO₂ storage device 18. Alternatively, to improve the efficiency of CO₂ loading and unloading, a plurality of catenary anchor leg mooring devices 11 are employed and fixed to the seabed with mooring anchor chains 15. The CO₂ is transferred from the first floating CO₂ storage device 9 to the catenary anchor leg mooring device 11 through the subsea CO₂ transmission pipelines 6 and the underwater riser 13. The first CO2 transport ship 7 is moored and connected to the catenary anchor leg mooring device 11 via a mooring line 14. The liquid CO₂ is transferred from the catenary anchor leg mooring device 11 to first CO₂ transport ship 7 through the floating hose 12. Alternatively, the CO₂ from the industrial activities 1 is collected by the CO₂ capture module 2 and then transmitted in liquid form through the subsea CO₂ transmission pipeline 6 to the second floating CO₂ storage device 18.

[0022] When the first CO₂ transport ship 7 reaches a designated sea area and unloading conditions are satisfied, the first CO₂ transport ship 7 berths at a CO₂ loading and unloading dock 21. The CO₂ is transferred through a CO₂ transfer system 22 to the onshore CO₂ storage terminal 3. The CO₂ is then conveyed through the onshore CO₂ transmission pipelines 5 to a first CO₂ injection module 23 and subsequently is injected into an onshore CO₂ storage site 24.

[0023] When the first floating CO₂ storage device 9 loaded with the CO₂ reaches the designated sea area, if the unloading conditions are not satisfied, the CO₂ is transferred to the onshore CO₂ storage terminal 3 through the underwater riser 13, the subsea CO₂ transmission pipeline 6, and the onshore CO₂ transmission pipeline 5 over long distances. Notably, the subsea CO₂ transmission pipeline 6 is pre-laid on the seabed. The CO₂ is then transferred through the onshore CO₂ transmission pipelines 5 to the first CO₂ injection module 23 and subsequently injected into the onshore CO₂ storage site 24. Alternatively, the long-distance CO₂ transmission is achieved through a jacket-type CO₂ pressurized transmission platform 19. Specifically, the first CO₂ transport ship 7 and the second floating CO₂ storage device 18 are separately moored and connected to the catenary anchor leg mooring device 11 via the mooring line 14. The CO₂ is transmitted to the catenary anchor leg mooring device 11 through the floating hose 12. Alternatively, the first CO₂ transport ship 7 and the second floating CO₂ storage device 18 are separately moored and connected to the soft-rigid arm anchor leg mooring device 16 through the transmission hose 17. The CO₂ is transmitted to the soft-rigid arm anchor leg mooring device 16 through the transmission hose 17. Subsequently, the CO₂ is transported from the catenary anchor leg mooring device 11 or the soft-rigid arm anchor leg mooring device 16 to the jacket-type CO₂ pressurized transmission platform 19 through the subsea CO₂ transmission pipeline 6 and the underwater riser 13. The CO₂ is pressurized by a CO₂ booster transmission module 20 and transmitted through the subsea CO₂ transmission pipeline 6 and the onshore CO₂ transmission pipeline 5 to the first CO₂ injection module 23 and subsequently is injected into the onshore CO₂ storage site 24.

[0024] To improve the unloading efficiency, the plurality of catenary anchor leg moorings devices 11 are employed. The first floating CO₂ storage device 9 is used as a transfer station for CO₂. Specifically, the CO₂ is transmitted from the second CO₂ transport ship 8 and the third CO₂ transport ship 10 to the first floating CO₂ storage device 9. Additionally, the first CO₂ transport ship 7 is moored and connected to catenary anchor leg mooring device 11 through the mooring line 14. The CO₂ is transmitted to the catenary anchor leg mooring device 11 via the floating hose 12 and subsequently is conveyed to the first floating CO₂ storage device 9 through the subsea CO₂ transmission pipeline 6 and the underwater riser 13. The CO₂ is transferred from the first floating CO₂ storage device 9 to the onshore CO₂ storage terminal 3 through the subsea CO₂ transmission pipeline 6, the underwater riser 13, and the onshore CO₂ transmission pipelines 5, transferred through the onshore CO₂ transmission pipeline 5 to the first CO₂ injection module 23, and injected into the onshore CO₂ storage site 24.

[0025] Many abandoned oil fields are suited offshore, in the sea. FIG. 2 is a schematic diagram showing a general layout of CO₂ undersea storage. As shown in FIG. 2, the CO₂ from industrial activities is collected by the CO₂ capture module 2 and stored in liquid form at the onshore CO₂ storage terminal 3. The CO₂ is then transported over a long distance to a submarine wellhead 26 for storage. The liquid CO₂ is transmitted to the onshore CO₂ loading arm 4 through the onshore CO₂ transmission pipeline 5 and then is offloaded to the first CO₂ transport ship 7. Alternatively, the CO₂ is transferred to the catenary anchor leg mooring device 11 via the subsea CO₂ transmission pipeline 6 and the underwater riser 13, and then is offloaded to the first CO₂ transport ship 7 through the floating hose 12. Alternatively, the CO₂ is transferred to the soft-rigid arm anchor leg mooring device 16 through the subsea CO₂ transmission pipeline 6 and the underwater riser 13, and then is offloaded to the first CO₂ transport ship 7 through the transmission hose 17. When the first CO₂ transport ship 7 arrives at the designated sea area and unloading conditions are satisfied, the first CO₂ transport ship 7 berths at a CO₂ loading and unloading dock 21. The CO₂ is transferred through a CO₂ transfer system 22 to the onshore CO₂ storage terminal 3. The subsea CO₂ transmission pipeline 6 is connected to the submarine wellhead 26. The CO₂ is conveyed to the first CO₂ injection module 23 and subsequently transmitted to the submarine CO₂ storage site 25 through the subsea CO₂ transmission pipeline 6 and the submarine wellhead 26.

[0026] To improve the storage and transmission efficiency of CO₂, the first floating CO₂ storage device 9 is disposed in the nearshore sea areas. CO₂ produced from industrial activities 1 is collected by a CO₂ capture module 2. The collected CO₂ is converted into liquid form and transmitted to the first floating CO₂ storage device 9 through the subsea CO₂ transmission pipeline 6, and then transmitted to the second CO₂ transport ship 8 and the third CO₂ transport ship 10. Alternatively, to improve the loading and unloading efficiency of CO₂, the plurality of catenary anchor leg mooring devices 11 are employed. The catenary anchor leg mooring device 11 is employed and fixed to the seabed via the mooring anchor chain 15. The CO₂ is transferred from the first floating CO₂ storage device 9 to the catenary anchor leg mooring device 11 through the subsea CO₂ transmission pipeline 6 and the underwater riser 13. The first CO₂ transport ship 7 is moored and connected to the catenary anchor leg mooring device 11 via the mooring line 14. The CO₂ is transferred from the catenary anchor leg mooring device 11 to the first CO₂ transport ship 7 via the floating hose 12. Alternatively, the CO₂ from the industrial activities 1 is collected by the CO₂ capture module 2 and converted into liquid form; the liquid CO₂ is transferred through the subsea CO₂ transmission pipeline 6 to the second floating CO₂ storage device 18.

[0027] When the first floating CO₂ storage device 9 loaded with the CO₂ arrives at the designated sea area, the CO₂ is transmitted to a second CO₂ injection module 28 disposed on a conduit-type CO₂ injection platform 27 through the underwater riser 13 and the subsea CO₂ transmission pipeline 6. Subsequently, the CO₂ is injected into the submarine CO₂ storage site 25 through the underwater riser 13 and the submarine wellhead 26.

[0028] The CO₂ is transferred from the second CO₂ transport ship 8 and the third CO₂ transport ships 10 to the first floating CO₂ storage device 9. Additionally, the first CO2 transport ship 7 is moored and connected to the catenary anchor leg mooring device 11 via the mooring line 14. The CO₂ is transferred to the catenary anchor leg mooring device 11 through the floating hose 12, and subsequently is transferred to the first floating CO₂ storage device 9 through the subsea pipeline 6 and the underwater riser 13. The CO₂ is transferred to the second CO₂ injection module 28 disposed on the conduit-type CO₂ injection platform through the underwater riser 13 and the subsea CO₂ transmission pipeline 6. Finally, the CO₂ is injected into the submarine CO₂ storage site 25 through the underwater riser 13 and the submarine wellhead 26.

[0029] The second CO₂ transport ships 8 and the third CO₂ transport ship 10 are separately moored and connected to the second floating CO₂ storage device 18. The second floating CO₂ storage device 18 is moored and connected to the catenary anchor leg mooring device 11 via the mooring line 14. The CO₂ is transmitted to the catenary anchor leg mooring devices 11 through the floating hose 12. Alternatively, the second floating CO₂ storage device 18 is moored and connected to the soft-rigid arm anchor leg mooring device 16 via the transmission hose 17, so that the CO₂ is transmitted from the second floating CO₂ storage device 18 to the soft-rigid arm anchor leg mooring device 16 through the transmission hose 17. The CO₂ is transmitted from the catenary anchor leg mooring device 11 or the soft-rigid arm anchor leg mooring device 16 to the second CO₂ injection module 28 disposed on the conduit-type CO₂ injection platform 27 through the underwater riser 13 and the subsea CO₂ transmission pipeline 6. The underwater riser 13 is connected to the submarine wellhead 26, so that the CO₂ is then injected into the submarine CO₂ storage site 25 through the underwater riser 13 and the submarine wellhead 26.

[0030] As shown in FIGS. 7-9, the disclosure provides a liquid CO₂ tank that is capable of self-recovered, self-regulating pressure release, and maintaining a suspended state. The liquid CO₂ tank comprises a tank body 95 used to store the liquid CO₂. The strength parameters of the tank body 95 is determined according to the depth at which the tank body will be submerged in the seawater. The liquid CO₂ tank comprises a pressure-controlled injection device 91, a pressure-controlled discharge device 92, a satellite positioning device 93, a nitrogen generation device 94, and a pressure-controlled relief device 96. The tank body 95 is capsule-shaped. The capsule-shape helps maintain the stability during the processes of sinking and floating, preventing the liquid CO₂ tank from overturning and facilitating better pressure control. The capsule shape of the tank body is combined with a symmetrical system and thus ensures that the center of gravity is centrally located, but with a slight bias towards the end where the discharge device is situated. The design causes the liquid CO₂ tank to sink vertically along the length of the tank body when submerged, maintaining the stability and orientation of the liquid CO₂ tank.

[0031] The tank body 95 is designed to withstand both the internal pressure and the external pressure exceeding 30bar. Preferably, the tank body 95 is capsule-shaped. The capsule-shape helps maintain the stability during the processes of sinking and floating, preventing the tank from overturning and facilitating better pressure control.

[0032] As the liquid CO₂ tank sinks deeper into the sea, the external pressure from the surrounding seawater increases. When the external pressure becomes greater than the internal pressure of the tank body 95, the pressure-controlled injection device 91 automatically opens in response to the pressure difference. Preferably, the pressure-controlled injection device is used to regulate the rate at which seawater enters the tank body. The regulation is controlled by the size of the opening of the pressure-controlled injection device. A difference between the internal pressure and the external pressure continues to increase as the liquid CO₂ tank sinks deeper. In addition, when a large amount of seawater has flowed into the liquid CO₂ tank, the internal pressure and the external pressure eventually equalize. At the point, the pressure-controlled injection device 91 automatically closes to prevent further seawater from entering the tank body. In addition, the Chinese patent "an industrial bus type LNG fuel security control device for ships" (Patent No. CN201721324589.6) provides a similar injection device. The disclosed pressure-controlled injection device 91 is adapted for use by determining the parameters through simple modifications and testing.

[0033] As the liquid CO₂ tank sinks to a depth of 1000 meters, the external pressure exerted by the surrounding seawater increases significantly. When the external pressure reaches the design pressure of the liquid CO₂ tank, the pressure-controlled discharge device 92 automatically opens in response to the external pressure. Preferably, the nitrogen gas is filled into the liquid CO₂ tank; the pressure-controlled discharge device comprises a gas escape device 97; the gas escape device 97 is used to prevent the liquid CO₂ tank from sinking again if the nitrogen gas escapes. The Chinese patent "an industrial bus type LNG fuel security control device for ships" (Patent No. CN201721324589.6) provides a similar discharge device. The disclosed discharge device 92 is adapted for use by determining the parameters through simple modifications and testing.

[0034] As the liquid CO₂ tank descends, the tank body is heated by the surrounding seawater. The heating causes the temperature of the liquid CO₂ inside the tank body to rise, thus increasing the internal pressure. When the internal pressure exceeds a certain level, the pressure-controlled relief device 96 automatically opens, so as to maintain the internal pressure at a safe level, specifically at 30 bar, by releasing excess pressure. To ensure the structural integrity of the tank body 95 and minimize the need for additional openings in the tank body 95, the pressure-controlled relief device 96 is disposed on the pressure-controlled discharge device 92. The pressure-controlled relief device 96 is similar to a relief device described in the Chinese patent CN202021137650.8, titled "a kind of LPG ship safety relief pipeline device". The disclosed pressure-controlled relief device 96 is adapted for use in the liquid CO₂ tank by determining the parameters through simple modifications and testing.

[0035] When the liquid CO₂ tank sinks to a depth of 1000 meters underwater, the external pressure from the surrounding seawater increases significantly. When the external pressure reaches the design pressure of the tank body 95, the nitrogen generation device 94 automatically activates in response to the external pressure. The nitrogen generation device 94 then generates nitrogen gas through a chemical reaction. Preferably, the nitrogen generation device 94 is similar to a device described in the Chinese patent titled "an emergency rescue device for sunken submarines and surface ships using chemical energy". The disclosed nitrogen generation device 94 is adapted for use by determining the parameters through simple modifications and testing.

[0036] The satellite positioning device 93 is used to locate the liquid CO₂ tank when the liquid CO₂ tank floats to the surface of the sea due to buoyancy.

[0037] The operation process of the liquid CO₂ tank is described in detail:
As shown in FIG. 10, the liquid CO₂ tank is deployed from a bottom hatch of a recovery vessel. The pressure-controlled discharge device 92 is oriented downward, so that the liquid CO₂ tank remains in a vertical orientation. Because the center of gravity is lower, the liquid CO₂ tank remains upright during operation. Since the liquid CO₂ tank is heavier than sea water, the liquid CO₂ tank sinks.

[0038] As the liquid CO₂ tank descends, the seawater at a temperature of above 0°C heats the tank body 95. The heating causes the temperature of the liquid CO₂ inside the liquid CO₂ tank to rise, thus increasing the internal pressure. To manage the increased internal pressure, the pressure-controlled relief device 96 automatically releases the internal pressure and maintain the internal pressure at 30 bar.

[0039] When the liquid CO₂ tank reaches a depth of 300 meters, the external pressure on the tank body 95 becomes 31 bar, which is greater than the internal pressure. To manage the external pressure, the pressure-controlled injection device 91 automatically opens, allowing the seawater to enter the liquid CO₂ tank.

[0040] As the seawater enters the tank body 95, the difference between the internal pressure and the external pressure is reduced. The descent speed of the liquid CO₂ tank is regulated by the resistance from the seawater. When the seawater resistance equals to the weight of the liquid CO₂ tank, the sinking speed stabilizes. The opening size of the pressure-controlled injection device 91 is controlled to regulate the flow rate of the seawater, so as to maintain the pressure difference within 30 bar.

[0041] When the liquid CO₂ tank sinks to a depth of 1000 meters underwater, the pressure difference is adjusted to between 20 - 30 bar or more by controlling the opening size of the pressure-controlled injection device 91. The pressure-controlled discharge device 92 then opens, allowing a large amount of seawater to flow into the liquid CO₂ tank, resulting in equalizing the internal pressure and the external pressure. Subsequently, the pressure-controlled injection device 91 is closed. As shown in FIG. 11, with the pressure difference at zero, the liquid CO₂ flows out of the liquid CO₂ tank due to gravity and dissolves in the seawater, achieving the storage goal at 1000 meters underwater.

[0042] At the same time, the nitrogen generation device 94 activates, producing nitrogen gas through a chemical reaction. The nitrogen gas, being less dense, fills the upper part of the interior of the liquid CO₂ tank, pushing out the seawater and making the liquid CO₂ tank buoyant. The liquid CO₂ tank starts to rise to the surface of the sea. The gas escape device 97 is used to prevent the liquid CO₂ tank from sinking again if nitrogen escapes.

[0043] As shown in FIG. 12, the tank body 95 floats to the surface of the sea due to buoyancy.

[0044] As shown in FIG. 13, the satellite positioning device 93 is used to locate the liquid CO₂ tank.

[0045] As shown in FIG. 14, the bottom hatch of the recovery vessel is then opened; the recovery vessel is used to retrieve the liquid CO₂ tank from the sea; and the liquid CO₂ tank is reused for further processing.

[0046] It will be obvious to those skilled in the art that changes and modifications may be made, and therefore, the aim in the appended claims is to cover all such changes and modifications.

Claims

1. A novel CO₂ maritime transshipment and storage system, comprising:

a. when loading conditions are satisfied, liquid CO₂ is transported from an onshore CO₂ storage terminal to a CO₂ loading device through an onshore pipeline; the CO₂ is then transferred to a CO₂ transport ship; when the CO₂ transport ship reaches a designated sea area, the liquid CO₂ is offloaded via a CO₂ transfer system, conveyed to a CO₂ injection module through the onshore pipeline, and then is injected into an onshore CO₂ storage site or a submarine CO₂ storage site;

when the loading conditions are not satisfied, an alternative procedure, step b or step c, is selected:

b. the liquid CO₂ is transported from the onshore CO₂ storage terminal to a floating CO₂ storage device through a subsea pipeline; the CO₂ transport ship is moored in an inline or side-by-side configuration with the floating CO₂ storage device; the CO₂ is offloaded from CO₂ transport ship to the floating CO₂ storage device via a hose; upon reaching the designated sea area, the CO₂ transport ship is moored in an inline or side-by-side configuration with the floating CO₂ storage device; the floating CO₂ storage device comprises a plurality of internal turrets; the CO₂ is transferred from the CO₂ transport ship to the floating CO₂ storage device through the hose; subsequently, the CO₂ is transmitted to an offshore CO₂ injection platform through the plurality of internal turrets, a subsea pipeline, and an underwater riser; finally, the CO₂ is injected into a submarine CO₂ storage site through a submarine wellhead, ensuring long-term storage; and

c. the CO₂ is transmitted from the onshore CO₂ storage terminal to the floating CO₂ storage device through the subsea pipeline; after the floating CO₂ storage device arrives at the designated sea area, the CO₂ is conveyed to the offshore CO₂ injection platform through the plurality of internal turrets, the subsea pipeline, and the underwater riser; finally, the CO₂ is injected into the submarine CO₂ storage site through a submarine wellhead, ensuring long-term storage.

2. The novel CO₂ maritime transshipment and storage system of claim 1,
wherein the step a, step b, or step c is performed as follows:

S1. injecting liquid CO₂ into a liquid CO₂ tank; where, the liquid CO₂ tank comprises a tank body used to store the liquid CO₂; the tank body comprises a thermal insulation layer; the liquid CO₂ tank further comprises a discharge tank and an injection device; the discharge tank and the injection device are disposed on a first end and a second end of the tank body, respectively; the injection device comprises a unidirectional valve; the center of gravity of the tank body is tilted towards the first end of the tank body; the liquid CO₂ tank further comprises a nitrogen generation device disposed inside the tank body, specifically disposed at the second end of the tank body; the discharge device comprises a pressure-controlled relief device; and the liquid CO₂ tank further comprises a pressure-controlled valve;

S2. transporting, by a ship, the liquid CO₂ tank to an ocean storage area;

S3. releasing the liquid CO₂ tank into the seawater; where, the center of gravity of the tank body is tilted towards the first end of the tank body; the liquid CO₂ tank sinks in a vertical position, with the first end of the tank body facing downward;

S4. opening the pressure-controlled relief device to release the internal pressure when the internal pressure reaches an activation pressure of the pressure-controlled relief device;

S5. opening the injection device to permit the seawater to flow into the liquid CO₂ tank when the external seawater pressure reaches the activation pressure of the injection device;

S6. fully opening both the injection device and the discharge device when the liquid CO₂ tank reaches a designated CO₂ storage depth, and closing the injection device when the liquid CO₂ tank is filled with the seawater; where, the injection device and the discharge device are actuated to an open state, permitting the release of the liquid CO₂ from the liquid CO₂ tank;

S7. activating the nitrogen generation device to produce nitrogen gas, and closing the discharge device to seal the liquid CO₂ tank after the seawater exit the liquid CO₂ tank; where, the nitrogen gas displaces the seawater from the liquid CO₂ tank, making the liquid CO₂ tank buoyant and causing the liquid CO₂ tank to float on the surface of the sea; and

S8. retrieving the liquid CO₂ tank floating on the surface of the sea due to buoyancy.

3. The deep-sea storage method of claim 2, wherein the liquid CO₂ tank achieves a center of gravity that is biased towards the first end of the tank body by attaching a fixed weight.

4. The deep-sea storage method of claim 2, wherein the liquid CO₂ tank further comprises a satellite positioning device used to locate the liquid CO₂ tank when the liquid CO₂ tank floats to the surface of the sea due to buoyancy.

5. The deep-sea storage method of claim 2, wherein the liquid CO₂ tank further comprises a position monitoring device used to determine a depth at which the liquid CO₂ tank has sunk; each of the injection device and the discharge device has a remote control mechanism; the remote control mechanisms allow the injection device and the discharge device to operate respectively when the liquid CO₂ tank sinks to a target depth as detected by the position monitoring device.

6. The deep-sea storage method of claim 2, wherein the liquid CO₂ tank has a maximum allowable pressure of 30 bar.

7. The deep-sea storage method of claim 2, wherein in S6, a minimum depth for CO₂ storage is 1000 meters underwater.

8. The deep-sea storage method of any one of claims 1-7, wherein when the CO₂ is in a liquid state, the pressure within a set of pipelines ranges from 0.4 MPa to 7.39 MPa; when the CO₂ is in a supercritical state, the CO₂ in the set of pipelines is maintained at temperatures above 31.3°C, with the pressure exceeding 7.39 MPa; when the CO₂ is in a gaseous state, the pressure within the set of pipelines ranges from 0 to 7.39 MPa; and
the CO₂ transport ship comprises a C-type tank for storage; and the CO₂ transport ship is used to contain the CO₂ at pressures ranging from 0.4 MPa to 2.1 MPa.

Drawing