A device and method for sequestering liquid carbon dioxide on the seabed

Abstract

This invention relates to a device and method for sequestering liquid carbon dioxide on the seabed, belonging to the field of carbon neutrality technology. The device includes a carbon storage tank with a carbon dioxide injection port at the top and several drainage holes spaced apart on the side near the bottom. The method includes the following steps: filling the carbon storage tank with seawater and sinking it into the sea; injecting liquid carbon dioxide from an offshore platform or ship into the carbon storage tank through a carbon dioxide injection pipeline, gradually displacing most of the seawater downwards, leaving a small portion of seawater, and then sealing the liquid carbon dioxide injection port. The small portion of seawater reacts with the liquid carbon dioxide to form carbon dioxide hydrate, thereby permanently sealing the liquid carbon dioxide and completely preventing the liquid carbon dioxide on the seabed from surfacing and escaping.

Description

Technical Field

[0001] This invention relates to the field of carbon neutrality technology, specifically to a device and method for sequestering liquid carbon dioxide on the seabed. Background Technology

[0002] Climate change, triggered by the rapid increase in atmospheric carbon dioxide levels in recent years, has been listed as the leading global environmental issue. With industrialization and socio-economic development, emissions of carbon dioxide and other greenhouse gases are continuously increasing.

[0003] Reducing atmospheric CO2 is a fundamental way to mitigate the greenhouse effect. Carbon Capture and Storage (CCS) technology is a key technology for effectively reducing carbon emissions and achieving low-carbon development, and it is of great significance for mitigating global warming. Currently, international CCS projects mainly involve injecting carbon dioxide into oil fields to improve oil recovery and directly injecting it underground or onto the seabed for storage. However, CO2-enhanced oil recovery and storage is limited by the distribution of oil and gas fields, resulting in a limited storage capacity and making it difficult to achieve large-scale CO2 storage. It is only suitable for short- to medium-term disposal. Deep saline aquifers are widely distributed, offering many encapsulation and storage mechanisms, but current understanding of these geological structures is limited, and there are many leakage pathways and unknown factors. Marine storage is currently the most promising storage method. Deep-sea storage requires injecting CO2 to depths below 3000 m, which is technically challenging. Shallow-to-medium seabed storage using CO2 hydrates lacks large-scale CO2 injection and conversion processes for hydrate formation, resulting in poor controllability. In addition, these open-access marine storage facilities also pose risks of impact on the marine environment and leakage.

[0004] In summary, there is currently a lack of devices and methods for large-scale sequestration of carbon dioxide on the seabed. Summary of the Invention

[0005] To address the aforementioned problems, the present invention aims to provide a device and method for sequestering liquid carbon dioxide on the seabed, thereby solving the current lack of devices and methods for large-scale sequestration of carbon dioxide on the seabed.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] In a first aspect, the present invention discloses a subsea liquid carbon dioxide sequestration device, comprising a carbon storage tank.

[0008] The top of the carbon storage box is provided with a carbon dioxide injection hole, and a switch valve is provided on the carbon dioxide injection hole.

[0009] The carbon storage box has several drain holes spaced apart on its side near the bottom.

[0010] The carbon dioxide injection port and the liquid drainage port are respectively connected to the internal cavity of the carbon storage tank.

[0011] Preferably, the carbon storage box is a container made of corrosion-resistant material.

[0012] Preferably, the carbon storage box has a rectangular or cylindrical structure.

[0013] When the carbon storage box has a cuboid structure, each side of the carbon storage box is provided with a drain hole.

[0014] When the carbon storage box has a cylindrical structure, four drain holes are provided at intervals on the side of the carbon storage box.

[0015] Secondly, this invention discloses a method for sequestering liquid carbon dioxide on the seabed, employing the aforementioned seabed liquid carbon dioxide sequestration device and carbon injection facility. The carbon injection facility is a vessel or offshore platform carrying liquid carbon dioxide, and is equipped with a liquid carbon dioxide outlet, which is fitted with an unloading valve. The method includes the following steps:

[0016] Step S1: Select a seabed storage area, place the carbon dioxide injection port of the carbon storage box facing upwards on the ocean surface of the seabed storage area, and inject seawater into the carbon storage box until the carbon storage box is full of seawater.

[0017] Step S2: Install carbon injection facilities on the sea surface of the seabed storage area, and connect the carbon dioxide liquid outlet of the carbon injection facilities to the carbon dioxide injection hole through a carbon dioxide injection pipeline. Then, sink the carbon storage box into the seabed storage area.

[0018] Step S3: Open the unloading valve, and the liquid carbon dioxide in the carbon injection facility is output from the liquid carbon dioxide outlet and flows into the carbon dioxide injection hole through the carbon dioxide injection pipeline;

[0019] Step S4: Open the switch valve on the carbon dioxide injection hole, and the liquid carbon dioxide in the carbon dioxide injection pipeline is injected into the carbon storage tank through the carbon dioxide injection hole. At the same time, the original seawater in the carbon storage tank is discharged from the drain hole on the side.

[0020] When the amount of liquid carbon dioxide injected into the carbon storage tank reaches the critical value of the total amount of liquid carbon dioxide injected, some seawater remains, the unloading valve is closed, and the flow of liquid carbon dioxide into the carbon dioxide injection pipeline is stopped.

[0021] Step S5: Close the switch valve on the carbon dioxide injection port, disconnect the connection between the carbon dioxide liquid outlet of the carbon injection facility and the carbon dioxide injection pipeline, connect a suction pump to the outer end of the carbon dioxide injection pipeline, and recover the liquid carbon dioxide in the carbon dioxide injection pipeline through the suction pump.

[0022] When the unloading valve is opened, liquid carbon dioxide in the carbon injection facility is output from the liquid carbon dioxide outlet; when the unloading valve is closed, the output of liquid carbon dioxide to the carbon dioxide injection pipeline stops.

[0023] In step S1, the carbon dioxide injection hole is kept open, allowing seawater to spontaneously flow into the carbon storage tank from the side drainage hole. At the same time, the carbon storage tank 1 gradually sinks and eventually fills the inner cavity of the carbon storage tank with seawater.

[0024] Preferably, the depth range of the seabed storage area is between 400 and 3000 meters below the sea surface.

[0025] Preferably, in step S4, when the carbon storage tank sinks to the seabed and approaches the seabed sediment, liquid carbon dioxide continues to be injected from the carbon dioxide injection hole, and the volume change rate of the injected liquid carbon dioxide is equal to the volume change rate of the original seawater in the carbon storage tank discharged from the side drain hole.

[0026] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0027] (I) The present invention discloses a device and method for sequestering liquid carbon dioxide on the seabed. The device includes a carbon storage tank, the top of which is provided with a carbon dioxide injection hole, and the side of which is provided with a number of drainage holes at intervals near the bottom. The method includes the following steps: filling the carbon storage tank with seawater and sinking it into the sea; injecting liquid carbon dioxide from an offshore platform or ship into the carbon storage tank through a carbon dioxide injection pipeline, gradually displacing most of the seawater downwards, leaving a small portion of seawater, and then sealing the liquid carbon dioxide injection hole. The small portion of seawater reacts with the liquid carbon dioxide to generate carbon dioxide hydrate on the seabed, thereby permanently sealing the liquid carbon dioxide and completely preventing the liquid carbon dioxide on the seabed from floating and escaping.

[0028] (ii) The subsea liquid carbon dioxide sequestration device and method disclosed in this invention can achieve permanent sequestration of carbon dioxide under current technical conditions, and is simple, fast, large-scale, stable in the long term, and has no impact on the marine environment.

[0029] Furthermore, the present invention also has the following advantages:

[0030] (1) The device has a simple structure and a mature casting process. During the submersion process, the upper and lower connecting holes ensure that the pressure inside and outside the device is the same, so the pressure requirement of the device is small. After the sealing device sinks to the seabed, liquid carbon dioxide is directly injected through the connecting pipeline, without the need to build an injection well. After the liquid carbon dioxide injection is completed, the connecting pipeline can be recycled.

[0031] (2) The liquid carbon dioxide injection process is the process of liquid carbon dioxide displacing seawater in the storage device. Compared with injection into sediment, this process has low flow resistance and high injection efficiency.

[0032] (3) After the liquid carbon dioxide is injected, the liquid carbon dioxide occupies most of the internal space of the storage device, so the carbon dioxide storage density is high. By building multiple large-volume storage devices, large-scale liquid carbon dioxide storage can be achieved.

[0033] (4) Unlike traditional geological storage methods, this invention stores liquid carbon dioxide by injecting it into a storage device. Since the density of liquid carbon dioxide in the storage area is less than that of seawater, the lower layer of seawater ensures that the liquid carbon dioxide cannot flow directly into the external seawater. After the liquid carbon dioxide is injected, it may escape into the seawater through a dissolution effect. At this time, carbon dioxide hydrate will spontaneously form in the drain hole to block the drain hole and prevent carbon dioxide leakage, thereby achieving long-term stable storage of liquid carbon dioxide.

[0034] (5) The injected liquid carbon dioxide does not come into direct contact with the external seawater, so it has no impact on the marine ecological environment. Attached Figure Description

[0035] Figure 1 This is a schematic diagram of the structure of the seabed liquid carbon dioxide storage device provided in Embodiment 1 of the present invention;

[0036] Figure 2 This is a schematic diagram of the seabed liquid carbon dioxide sequestration and injection process provided in Embodiment 2 of the present invention.

[0037] Explanation of reference numerals in the attached diagram: 1-carbon storage tank, 11-carbon dioxide injection hole, 12-drainage hole;

[0038] 2-Carbon injection facility, 21-Carbon dioxide injection pipeline. Detailed Implementation

[0039] Exemplary embodiments of the invention will now be described in more detail with reference to the accompanying drawings. While exemplary embodiments of the invention are shown in the drawings, it should be understood that the invention can be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided to enable a more thorough understanding of the invention and to fully convey the scope of the invention to those skilled in the art.

[0040] Addressing the issue that carbon dioxide, with a density lower than seawater in the mid-to-deep seabed (depth less than 3000 meters), will escape into the ocean in the form of plumes, failing to meet the requirements for long-term stable storage, this invention proposes a seabed liquid carbon dioxide sequestration device. The device includes a carbon storage tank with a liquid carbon dioxide injection port and several drainage ports connected to seawater. The method includes the following steps: filling the carbon storage tank with seawater and submerging it in the sea; injecting liquid carbon dioxide from an offshore platform or vessel into the carbon storage tank through a carbon dioxide injection pipeline, gradually displacing most of the seawater downwards, leaving a small portion of seawater; then sealing the liquid carbon dioxide injection port, where the remaining seawater reacts with the liquid carbon dioxide to form carbon dioxide hydrates on the seabed, thereby permanently sealing the liquid carbon dioxide and completely preventing its escape from the seabed.

[0041] Example 1: A Submarine Liquid Carbon Dioxide Sequestration Device

[0042] Embodiment 1 of the present invention provides a subsea liquid carbon dioxide storage device, the structure of which will be described in detail below with reference to the accompanying drawings.

[0043] refer to Figure 1 The subsea liquid carbon dioxide sequestration device includes a carbon storage tank 1.

[0044] The top of the carbon storage box 1 is provided with a carbon dioxide injection hole 11, and a switch valve is provided on the carbon dioxide injection hole 11.

[0045] The carbon storage box 1 has several drain holes 12 spaced apart on its side near the bottom.

[0046] Carbon dioxide injection hole 11 and drain hole 12 are respectively connected to the internal cavity of the carbon storage tank 1;

[0047] Among them, the carbon dioxide injection hole 11 is used to inject liquid containing carbon dioxide;

[0048] Drain hole 12 is used for gas communication and for discharging liquid carbon dioxide and carbon dioxide hydrate generated by the reaction of residual seawater.

[0049] Preferably, the carbon storage box 1 is a storage container made of corrosion-resistant material.

[0050] Preferably, the carbon storage box 1 has a rectangular or cylindrical structure.

[0051] When the carbon storage box 1 has a cuboid structure, each side of the carbon storage box 1 is provided with a drain hole 12.

[0052] When the carbon storage box 1 has a cylindrical structure, four drain holes 12 are provided on the side of the carbon storage box 1 at intervals.

[0053] Example 2: A method for sequestering liquid carbon dioxide on the seabed

[0054] Embodiment 2 of the present invention provides a method for sequestering liquid carbon dioxide on the seabed, using the sequestering device for liquid carbon dioxide in Embodiment 1, with reference to... Figure 2 The method includes the following steps:

[0055] Step S1: Select a seabed storage area, place the carbon dioxide injection port 11 of the carbon storage box 1 facing upward on the ocean surface of the seabed storage area, and inject seawater into the carbon storage box 1 until the carbon storage box 1 is full of seawater;

[0056] Step S2: Install carbon injection facility 2 on the sea surface of the seabed storage area, and connect the carbon dioxide liquid outlet of carbon injection facility 2 to the carbon dioxide injection hole 11 through carbon dioxide injection pipeline 21 in a detachable manner, and then sink the carbon storage box 1 into the seabed storage area.

[0057] Among them, carbon injection facility 2 is a vessel carrying liquid carbon dioxide. Carbon injection facility 2 is equipped with a liquid carbon dioxide outlet. The liquid carbon dioxide outlet is equipped with an unloading valve. When the unloading valve is opened, the liquid carbon dioxide in carbon injection facility 2 is output from the liquid carbon dioxide outlet. When the unloading valve is closed, the output of liquid carbon dioxide to carbon dioxide injection pipeline 21 stops.

[0058] "Setting up carbon injection facility 2 on the sea surface of the seabed storage area" includes the following two situations:

[0059] When the carbon injection facility 2 is a vessel, it is driven to the sea surface of the seabed storage area.

[0060] When the carbon injection facility 2 is an offshore platform, the offshore platform is built directly on the sea surface of the seabed storage area.

[0061] Step S3: Open the unloading valve, and the liquid carbon dioxide in the carbon injection facility 2 is output from the liquid carbon dioxide outlet and flows into the carbon dioxide injection hole 11 through the carbon dioxide injection pipeline 21.

[0062] Step S4: Open the switch valve on the carbon dioxide injection hole 11. The liquid carbon dioxide in the carbon dioxide injection pipeline 21 is injected into the carbon storage tank 1 through the carbon dioxide injection hole 11. At the same time, the original seawater in the carbon storage tank 1 is discharged from the drain hole 12 on the side.

[0063] When the liquid carbon dioxide injected into the carbon storage tank 1 reaches the critical value of the total amount of liquid carbon dioxide injected, some seawater remains, the unloading valve is closed, and the flow of liquid carbon dioxide into the carbon dioxide injection pipeline 21 is stopped.

[0064] Step S5: Close the switch valve on the carbon dioxide injection port 11, disconnect the connection between the carbon dioxide liquid outlet of the carbon dioxide injection facility 2 and the carbon dioxide injection pipeline 21, connect a suction pump to the outer end of the carbon dioxide injection pipeline 21, and recover the liquid carbon dioxide in the carbon dioxide injection pipeline 21 through the suction pump.

[0065] Preferably, in step S1, the carbon dioxide injection hole 11 is kept open, allowing seawater to spontaneously flow into the carbon storage tank 1 from the side drainage hole 12, while the carbon storage tank 1 gradually sinks and eventually fills the inner cavity of the carbon storage tank 1 with seawater.

[0066] To ensure that the carbon dioxide exists in liquid form and that the density of the liquid carbon dioxide is less than the density of seawater corresponding to the burial depth, preferably, the depth range of the seabed storage area is between 400 and 3000 meters below the sea surface.

[0067] Preferably, in step S4, when the carbon storage tank 1 sinks to the seabed and approaches the seabed sediment, liquid carbon dioxide continues to be injected from the carbon dioxide injection hole 11, and the volume change rate of the injected liquid carbon dioxide is equal to the volume change rate of the original seawater in the carbon storage tank 1 discharged from the side drain hole 12.

[0068] Preferably, the critical value of the total amount of liquid carbon dioxide injected is the volume of the carbon storage box 1 when the lowest point of the remaining seawater just reaches the drain hole 12.

[0069] When the carbon storage tank 1 has a cuboid structure, in step S4, the injection of liquid carbon dioxide stops when the liquid surface of the original seawater in the carbon storage tank 1 approaches the drain hole 12. The remaining volume of the critical value of the total liquid carbon dioxide injection in this case... Determined according to the following formula:

[0070]

[0071] In the formula, The length of the inner cavity of the carbon storage box 1;

[0072] The width of the inner cavity of the carbon storage box 1;

[0073] It is the vertical height between the carbon dioxide injection hole 11 and the drain hole 12.

[0074] Similarly, when the carbon storage tank 1 has a cylindrical structure, in step S4, the injection of liquid carbon dioxide stops when the liquid surface of the original seawater in the carbon storage tank 1 approaches the drain hole 12. The remaining volume of the critical value of the total amount of liquid carbon dioxide injected under this condition... Determined according to the following formula:

[0075]

[0076] In the formula, The radius of the inner cavity of the carbon storage box 1;

[0077] It is the vertical height between the carbon dioxide injection hole 11 and the drain hole 12.

[0078] To ensure that the carbon storage tank 1 continues to sink to the sea surface in the seabed storage area, the average density of the carbon storage tank 1 during the liquid carbon dioxide injection process is... The density of seawater is greater than that of the seabed storage area. The calculation formula is as follows:

[0079]

[0080] In the formula, This is the net weight of carbon storage box 1;

[0081] This refers to the density of liquid carbon dioxide under the corresponding temperature and pressure conditions in the seabed storage area.

[0082] This refers to the total volume of liquid carbon dioxide injected.

[0083] The density of seawater in the seabed storage area

[0084] This represents the volume of seawater remaining in carbon storage tank 1 after carbon dioxide injection is completed.

[0085] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for sequestering liquid carbon dioxide on the seabed, using a liquid carbon dioxide sequestration device and carbon injection facility (2). in, The subsea liquid carbon dioxide storage device includes a carbon storage tank (1), the top of the carbon storage tank (1) is provided with a carbon dioxide injection hole (11), and the carbon dioxide injection hole (11) is provided with a switch valve; a number of drain holes (12) are provided at intervals on the side of the carbon storage tank (1) near the bottom, and the carbon dioxide injection hole (11) and the drain holes (12) are respectively connected to the internal cavity of the carbon storage tank (1); The carbon injection facility (2) is a ship or offshore platform carrying liquid carbon dioxide. The carbon injection facility (2) is provided with a liquid carbon dioxide outlet and the liquid carbon dioxide outlet is equipped with an unloading valve. Its features include: Step S1: Select a seabed storage area, place the carbon dioxide injection hole (11) of the carbon storage box (1) facing upward on the ocean surface of the seabed storage area, and inject seawater into the carbon storage box (1) until the carbon storage box (1) is full of seawater. Step S2: Set up a carbon injection facility (2) on the sea surface of the seabed storage area, and connect the carbon dioxide liquid outlet of the carbon injection facility (2) to the carbon dioxide injection hole (11) through the carbon dioxide injection pipeline (21) in a detachable manner, and then sink the carbon storage box (1) into the seabed storage area. Step S3: Open the unloading valve, and the liquid carbon dioxide in the carbon injection facility (2) is output from the liquid carbon dioxide outlet and flows into the carbon dioxide injection hole (11) through the carbon dioxide injection pipeline (21). Step S4: Open the switch valve on the carbon dioxide injection hole (11), and the liquid carbon dioxide in the carbon dioxide injection pipeline (21) is injected into the carbon storage tank (1) through the carbon dioxide injection hole (11). At the same time, the original seawater in the carbon storage tank (1) is discharged from the drain hole (12) on the side. When the liquid carbon dioxide injected into the carbon storage tank (1) reaches the critical value of the total amount of liquid carbon dioxide injected, some seawater is left behind, the unloading valve is closed, and the liquid carbon dioxide is stopped from flowing out of the carbon dioxide injection pipeline (21). Step S5: Close the switch valve on the carbon dioxide injection hole (11), disconnect the connection between the carbon dioxide liquid outlet of the carbon injection facility (2) and the carbon dioxide injection pipeline (21), connect the suction pump to the outer end of the carbon dioxide injection pipeline (21), and recover the liquid carbon dioxide in the carbon dioxide injection pipeline (21) through the suction pump.

2. The method for sequestering liquid carbon dioxide on the seabed according to claim 1, characterized in that, When the unloading valve is opened, the liquid carbon dioxide in the carbon injection facility (2) is output from the liquid carbon dioxide outlet; when the unloading valve is closed, the output of liquid carbon dioxide to the carbon dioxide injection pipeline (21) is stopped.

3. The method for sequestering liquid carbon dioxide on the seabed according to claim 1, characterized in that, In step S1, the carbon dioxide injection hole (11) is kept open, allowing seawater to spontaneously flow into the carbon storage box (1) from the side drain hole (12), while the carbon storage box (1) gradually sinks and eventually the inner cavity of the carbon storage box (1) is filled with seawater.

4. The method for sequestering liquid carbon dioxide on the seabed according to claim 1, characterized in that, The depth range of the seabed storage area is between 400 and 3000 meters below the sea surface.

5. The method for sequestering liquid carbon dioxide on the seabed according to claim 1, characterized in that, In step S4, when the carbon storage tank (1) sinks into the seabed and approaches the seabed sediment, liquid carbon dioxide continues to be injected from the carbon dioxide injection hole (11), and the volume change rate of the injected liquid carbon dioxide is equal to the volume change rate of the original seawater in the carbon storage tank (1) discharged from the side drain hole (12).

6. The method for sequestering liquid carbon dioxide on the seabed according to claim 1, characterized in that, The carbon storage box (1) is a storage container made of corrosion-resistant material.

7. The method for sequestering liquid carbon dioxide on the seabed according to claim 1, characterized in that, The carbon storage box (1) has a rectangular or cylindrical structure.

8. The method for sequestering liquid carbon dioxide on the seabed according to claim 7, characterized in that, When the carbon storage box (1) has a cuboid structure, each side of the carbon storage box (1) is provided with a drain hole (12).

9. The method for sequestering liquid carbon dioxide on the seabed according to claim 7, characterized in that, When the carbon storage box (1) has a cylindrical structure, four drain holes (12) are provided on the side of the carbon storage box (1) at intervals.

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