Seabed liquid carbon dioxide sealing device and method

Abstract

The invention relates to a seabed liquid carbon dioxide sealing device and method, and belongs to the technical field of carbon neutralizer.The device comprises a carbon storage box, a carbon dioxide injection hole is formed in the top of the carbon storage box, and a plurality of liquid drainage holes are formed in the position, close to the bottom, of the side face of the carbon storage box at intervals; the method comprises the following steps: filling the carbon storage box with seawater and then sinking into the sea; liquid carbon dioxide of an offshore platform or a ship is injected into the carbon storage box through the carbon dioxide injection pipeline, most seawater is gradually replaced downwards, after a small part of seawater is left, the liquid carbon dioxide injection hole is blocked, and the small part of seawater reacts with the liquid carbon dioxide to generate carbon dioxide hydrate; therefore, liquid carbon dioxide is permanently blocked, and floating and dissipation of seabed liquid carbon dioxide are thoroughly prevented.

Description

Technical Field

[0001] The present invention relates to the field of carbon neutrality technology, and specifically to a submarine liquid carbon dioxide storage device and method. Background Art

[0002] In recent years, the global climate change problem caused by the sharp increase in carbon dioxide content in the atmosphere has also been listed as the top global environmental problem. With the progress of industrialization and the development of social economy, the emission of carbon dioxide and other greenhouse gases is constantly increasing.

[0003] Reducing CO2 in the atmosphere is the fundamental way to improve the greenhouse effect. Carbon capture and storage (CCS) technology is a key technology to effectively reduce carbon emissions and achieve low-carbon development, and is of great significance to mitigating global warming. At present, the carbon capture and storage projects carried out internationally mainly inject carbon dioxide into oil fields to improve the recovery rate of oil fields and directly inject it into the ground or seabed for storage. Carbon dioxide flooding storage is limited by the distribution of oil and gas fields, and the storage volume is limited. It is difficult to fundamentally achieve large-scale carbon dioxide storage, and it is only suitable for medium- and short-term disposal. Deep saline layers are widely distributed, and there are many optional enclosures and storage mechanisms, but the current understanding of this type of geological structure is limited, and there are many leakage pathways and unknown factors. Marine storage is currently the most promising storage method. Among them, deep-sea storage requires carbon dioxide to be injected into the seabed below 3000 m, which is difficult to implement; shallow and medium seabed storage in the form of carbon dioxide hydrates lacks large-scale carbon dioxide injection and conversion to hydrate technology, and has poor controllability. In addition, these open ocean storages also pose impacts to the marine environment and risks of leakage.

[0004] In short, there is currently a lack of equipment and methods for storing carbon dioxide on the seabed on a large scale. Summary of the invention

[0005] In view of the above problems, the purpose of the present invention is to provide a device and method for storing liquid carbon dioxide on the seabed, so as to solve the problem that there is currently a lack of devices and methods for storing carbon dioxide on the seabed on a large scale.

[0006] To achieve the above object, the present invention adopts the following technical solutions: In a first aspect, the present invention discloses a subsea liquid carbon dioxide storage device, comprising a carbon storage box, A carbon dioxide injection hole is provided on the top of the carbon storage box, and a switch valve is provided on the carbon dioxide injection hole; The side of the carbon storage box is provided with a plurality of drainage holes at intervals near the bottom. The carbon dioxide injection hole and the liquid discharge hole are respectively communicated with the internal cavity of the carbon storage box.

[0007] Preferably, the carbon storage box is a reservoir made of corrosion-resistant material.

[0008] Preferably, the carbon storage box has a rectangular parallelepiped or cylindrical structure.

[0009] When the structure of the carbon storage box is a rectangular parallelepiped, each side surface of the carbon storage box is respectively provided with a drainage hole.

[0010] When the structure of the carbon storage box is a cylinder, four drainage holes are arranged at intervals on the side of the carbon storage box.

[0011] In a second aspect, the present invention discloses a method for storing subsea liquid carbon dioxide, using the above-mentioned subsea liquid carbon dioxide storage device and carbon injection facility, wherein the carbon injection facility is a ship or an offshore platform carrying liquid carbon dioxide, and the carbon injection facility is provided with a carbon dioxide liquid outlet, and the carbon dioxide liquid outlet is equipped with an unloading valve; the method comprises the following steps: Step S1: selecting a seabed storage area, placing the carbon storage box with the carbon dioxide injection hole facing upward on the ocean surface of the seabed storage area, and injecting seawater into the carbon storage box until the seawater fills the carbon storage box; Step S2: a carbon injection facility is set on the sea surface of the seabed storage area, and the carbon dioxide liquid outlet of the carbon injection facility is detachably connected to the carbon dioxide injection hole through a carbon dioxide injection pipeline, and then the carbon storage box is sunk into the seabed storage area; Step S3: opening the unloading valve, and the liquid carbon dioxide in the carbon injection facility is output from the carbon dioxide liquid outlet and flows into the carbon dioxide injection hole through the carbon dioxide injection pipeline; Step S4: opening the switch valve on the carbon dioxide injection hole, and injecting the liquid carbon dioxide in the carbon dioxide injection pipeline into the carbon storage box through the carbon dioxide injection hole, while the original seawater in the carbon storage box is discharged from the drainage hole on the side; When the liquid carbon dioxide injected into the carbon storage tank reaches a critical value of the total amount of liquid carbon dioxide injected, part of the 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; Step S5: close the switch valve on the carbon dioxide injection hole, dismantle 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.

[0012] When the unloading valve is opened, the liquid carbon dioxide in the carbon injection facility is output from the carbon dioxide liquid outlet; when the unloading valve is closed, the output of liquid carbon dioxide to the carbon dioxide injection pipeline is stopped.

[0013] Wherein, in step S1, the carbon dioxide injection hole is kept open, so that seawater spontaneously flows into the carbon storage box from the drainage hole on the side, and at the same time, the carbon storage box 1 as a whole gradually sinks and finally the inner cavity of the carbon storage box is filled with seawater.

[0014] Preferably, the depth range of the seabed storage area is between 400-3000 meters below the sea surface.

[0015] Preferably, in step S4, when the carbon storage box sinks to the seabed and approaches the seabed sediment, the injection of liquid carbon dioxide from the carbon dioxide injection hole is continued, and the volume change rate of the liquid carbon dioxide injection is equal to the volume change rate of the original seawater in the carbon storage box discharged from the side drainage hole.

[0016] Compared with the prior art, the present invention has the following beneficial effects: (I) The present invention discloses a device and method for storing liquid carbon dioxide on the seabed, wherein the device comprises a carbon storage box, a carbon dioxide injection hole is arranged on the top of the carbon storage box, and a plurality of drainage holes are arranged at intervals on the side of the carbon storage box near the bottom. The method comprises the steps of: filling the carbon storage box with seawater and sinking it into the sea; injecting liquid carbon dioxide from an offshore platform or a ship into the carbon storage box through a carbon dioxide injection pipeline, gradually displacing most of the seawater downward, leaving a small portion of seawater, and then blocking the liquid carbon dioxide injection hole, wherein the small portion of seawater reacts with the liquid carbon dioxide to generate carbon dioxide hydrate on the seabed, thereby permanently blocking the liquid carbon dioxide and completely preventing the liquid carbon dioxide on the seabed from floating up and escaping.

[0017] (ii) The submarine liquid carbon dioxide storage device and method disclosed in the present invention can achieve permanent storage of carbon dioxide under current technical conditions, and is simple, fast, large-scale, long-term stable, and has no impact on the marine environment.

[0018] In addition, the present invention also has the following advantages: (1) The device has a simple structure and a mature casting process. During the submergence of the device, the upper and lower connecting holes ensure that the pressure inside and outside the device is the same, so the device has a small pressure requirement. After the storage 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 injection of liquid carbon dioxide is completed, the connecting pipeline can be recycled.

[0019] (2) The liquid carbon dioxide injection process is the process of using liquid carbon dioxide to displace seawater in the storage device. Compared with injection into sediments, this process has low flow resistance and high injection efficiency.

[0020] (3) After the injection of liquid carbon dioxide is completed, 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.

[0021] (4) Different from the traditional geological storage method, this invention seals the liquid carbon dioxide by injecting it into the storage device. Since the density of liquid carbon dioxide in the storage area is lower than that of seawater, the lower seawater can ensure 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 the dissolution effect. At this time, carbon dioxide hydrates will spontaneously form in the drainage holes to block the drainage holes and prevent carbon dioxide from leaking, thereby achieving long-term and stable storage of liquid carbon dioxide.

[0022] (5) The injected liquid carbon dioxide does not come into direct contact with external seawater and therefore has no impact on the marine ecological environment. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 is a schematic structural diagram of a submarine liquid carbon dioxide storage device provided in Example 1 of the present invention; Figure 2 It is a schematic diagram of the seabed liquid carbon dioxide storage and injection process provided in Example 2 of the present invention.

[0024] Description of reference numerals: 1-carbon storage box, 11-carbon dioxide injection hole 11, 12-liquid discharge hole; 2-Carbon injection facility, 21-Carbon dioxide injection pipeline. DETAILED DESCRIPTION

[0025] The exemplary embodiments of the present invention will be described in more detail below with reference to the accompanying drawings. Although the exemplary embodiments of the present invention are shown in the accompanying drawings, it should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments described herein. On the contrary, these embodiments are provided in order to enable a more thorough understanding of the present invention and to fully convey the scope of the present invention to those skilled in the art.

[0026] The density of carbon dioxide at the mid-deep seabed (depth less than 3,000 meters) is lower than that of seawater, and it will escape into the ocean water in the form of plumes, which cannot meet the problem of long-term stable storage. The present invention proposes a seabed liquid carbon dioxide storage device, wherein the device includes a carbon storage box, and the carbon storage box is provided with a liquid carbon dioxide injection hole and a plurality of drainage holes connected to seawater. The method includes the steps of: filling the carbon storage box with seawater and sinking it into the sea; injecting liquid carbon dioxide from an offshore platform or a ship into the carbon storage box through a carbon dioxide injection pipeline, gradually displacing most of the seawater downward, leaving a small part of the seawater, and then blocking the liquid carbon dioxide injection hole, wherein a small part of the seawater reacts with the liquid carbon dioxide to generate carbon dioxide hydrates on the seabed, thereby permanently blocking the liquid carbon dioxide and completely preventing the liquid carbon dioxide on the seabed from floating up and escaping.

[0027] Example 1: A submarine liquid carbon dioxide storage device Embodiment 1 of the present invention provides a submarine liquid carbon dioxide storage device, and its structure is described in detail below with reference to the accompanying drawings.

[0028] refer to Figure 1 The submarine liquid carbon dioxide storage device comprises a carbon storage box 1, The top of the carbon storage box 1 is provided with a carbon dioxide injection hole 11, and the carbon dioxide injection hole 11 is provided with a switch valve; The side of the carbon storage box 1 is provided with a plurality of drainage holes 12 at intervals near the bottom. The carbon dioxide injection hole 11 and the liquid discharge hole 12 are respectively connected to the internal cavity of the carbon storage box 1; Wherein, the carbon dioxide injection hole 11 is used to inject liquid containing carbon dioxide; The drain hole 12 is used for gas communication and for discharging carbon dioxide hydrate generated by the reaction of liquid carbon dioxide and part of the remaining seawater.

[0029] Preferably, the carbon storage box 1 is a storage container made of corrosion-resistant material.

[0030] Preferably, the carbon storage box 1 has a rectangular parallelepiped or cylindrical structure.

[0031] When the structure of the carbon storage box 1 is a rectangular parallelepiped, each side surface of the carbon storage box 1 is respectively provided with a drainage hole 12 .

[0032] When the structure of the carbon storage box 1 is a cylinder, four drainage holes 12 are arranged at intervals on the side surface of the carbon storage box 1 .

[0033] Example 2: A method for storing subsea liquid carbon dioxide Embodiment 2 of the present invention provides a method for storing subsea liquid carbon dioxide, using the subsea liquid carbon dioxide storage device of embodiment 1, referring to Figure 2 , the method comprises the following steps: Step S1: Select a seabed storage area, place the carbon storage box 1 with the carbon dioxide injection hole 11 facing upward on the ocean surface of the seabed storage area, and inject seawater into the carbon storage box 1 until the seawater fills the carbon storage box 1; Step S2: a carbon injection facility 2 is arranged on the sea surface of the seabed storage area, and the carbon dioxide liquid outlet of the carbon injection facility 2 is detachably connected to the carbon dioxide injection hole 11 through the carbon dioxide injection pipeline 21, and then the carbon storage box 1 is sunk into the seabed storage area; Among them, the carbon injection facility 2 is a ship carrying liquid carbon dioxide. The carbon injection facility 2 is provided with a carbon dioxide liquid outlet, and the carbon dioxide liquid outlet is equipped with an unloading valve. When the unloading valve is opened, the liquid carbon dioxide in the carbon injection facility 2 is output from the carbon dioxide liquid outlet; when the unloading valve is closed, the output of liquid carbon dioxide to the carbon dioxide injection pipeline 21 is stopped.

[0034] “Providing a carbon injection facility 2 on the sea surface of the said seabed storage area” includes the following two situations: When the carbon injection facility 2 is a ship, the carbon injection facility 2 is driven to the sea surface of the seabed sealing area; When the carbon injection facility 2 is an offshore platform, the offshore platform is directly built on the sea surface of the seabed storage area.

[0035] Step S3: Open the unloading valve, and the liquid carbon dioxide in the carbon injection facility 2 is output from the carbon dioxide liquid outlet and flows into the carbon dioxide injection hole 11 through the carbon dioxide injection pipeline 21; Step S4: opening the switch valve on the carbon dioxide injection hole 11, and injecting the liquid carbon dioxide in the carbon dioxide injection pipeline 21 into the carbon storage box 1 through the carbon dioxide injection hole 11, while the original seawater in the carbon storage box 1 is discharged from the side drainage hole 12; 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, part of the seawater is left, 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, dismantle the connection between the carbon dioxide liquid outlet of the carbon 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.

[0036] Preferably, in step S1, the carbon dioxide injection hole 11 is kept open, so that seawater spontaneously flows into the carbon storage box 1 from the side drainage hole 12, and the carbon storage box 1 as a whole gradually sinks and finally the inner cavity of the carbon storage box 1 is filled with seawater.

[0037] In order to ensure that carbon dioxide exists in liquid form and the density of liquid carbon dioxide is less than the density of seawater corresponding to the storage depth, preferably, the depth range of the seabed storage area is between 400-3000 meters below the sea surface.

[0038] Preferably, in step S4, when the carbon storage box 1 sinks to the seabed and approaches the seabed sediment, the injection of liquid carbon dioxide from the carbon dioxide injection hole 11 is continued, and the volume change rate of the liquid carbon dioxide injection is equal to the volume change rate of the original seawater in the carbon storage box 1 discharged from the side drainage hole 12.

[0039] 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 depth of the remaining seawater just reaches the drainage hole 12.

[0040] When the structure of the carbon storage box 1 is a rectangular parallelepiped, in step S4, the injection of liquid carbon dioxide is stopped when the liquid surface of the original seawater in the carbon storage box 1 approaches the drainage hole 12. In this case, the remaining volume of the critical value of the total amount of liquid carbon dioxide injected is Determine as follows:

[0041] In the formula, is the length of the inner cavity of the carbon storage box 1; is the width of the inner cavity of the carbon storage box 1; It is the vertical height between the carbon dioxide injection hole 11 and the drainage hole 12.

[0042] Similarly, when the structure of the carbon storage box 1 is cylindrical, in step S4, the injection of liquid carbon dioxide is stopped when the liquid surface of the original seawater in the carbon storage box 1 approaches the drain hole 12. In this case, the remaining volume of the critical value of the total amount of liquid carbon dioxide injected is Determine as follows:

[0043] In the formula, is the radius of the inner cavity of the carbon storage box 1; It is the vertical height between the carbon dioxide injection hole 11 and the drainage hole 12.

[0044] In order to ensure that the sea level in the carbon storage tank 1 continues to sink in the seafloor storage area, during the injection of liquid carbon dioxide, the average density of the carbon storage tank 1 Greater than the density of seawater in the seafloor storage area , and its calculation formula is:

[0045] In the formula, is the net weight of the carbon storage box 1; is the density of liquid carbon dioxide under the temperature and pressure conditions of the seafloor storage area; is the total volume of liquid carbon dioxide injected; is the density of seawater in the seafloor storage area It is the volume of seawater remaining in the carbon storage tank 1 after the carbon dioxide injection is completed.

[0046] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A submarine liquid carbon dioxide storage device, characterized in that: It includes a carbon storage box (1), The top of the carbon storage box (1) is provided with a carbon dioxide injection hole (11), and the carbon dioxide injection hole (11) is provided with a switch valve; A plurality of drainage holes (12) are arranged at intervals on the side of the carbon storage box (1) near the bottom. The carbon dioxide injection hole (11) and the liquid discharge hole (12) are respectively connected to the internal cavity of the carbon storage box (1).

2. The submarine liquid carbon dioxide storage device according to claim 1, characterized in that: The carbon storage box (1) is a storage container made of corrosion-resistant material.

3. The submarine liquid carbon dioxide storage device according to claim 1, characterized in that: The carbon storage box (1) has a rectangular or cylindrical structure.

4. The submarine liquid carbon dioxide storage device according to claim 3 is characterized in that: When the structure of the carbon storage box (1) is a rectangular parallelepiped, each side surface of the carbon storage box (1) is respectively provided with a liquid drainage hole (12).

5. The submarine liquid carbon dioxide storage device according to claim 3, characterized in that: When the structure of the carbon storage box (1) is a cylinder, four drainage holes (12) are arranged at intervals on the side surface of the carbon storage box (1).

6. A method for storing subsea liquid carbon dioxide, using the subsea liquid carbon dioxide storage device and carbon injection facility (2) as claimed in any one of claims 1 to 5, wherein: The carbon injection facility (2) is a vessel or an offshore platform carrying liquid carbon dioxide, and the carbon injection facility (2) is provided with a carbon dioxide liquid outlet, and the carbon dioxide liquid outlet is equipped with an unloading valve; The invention is characterized by comprising: Step S1: selecting a seabed storage area, placing the carbon dioxide injection hole (11) of the carbon storage box (1) upward on the ocean surface of the seabed storage area, and injecting seawater into the carbon storage box (1) until the seawater fills the carbon storage box (1); Step S2: a carbon injection facility (2) is arranged on the sea surface of the seabed storage area, the carbon dioxide liquid outlet of the carbon injection facility (2) is detachably connected to the carbon dioxide injection hole (11) via a carbon dioxide injection pipeline (21), and then the carbon storage box (1) is sunk into the seabed storage area; Step S3: opening the unloading valve, and the liquid carbon dioxide in the carbon injection facility (2) is discharged from the carbon dioxide liquid outlet and flows into the carbon dioxide injection hole (11) through the carbon dioxide injection pipeline (21); Step S4: opening the switch valve on the carbon dioxide injection hole (11), and injecting the liquid carbon dioxide in the carbon dioxide injection pipeline (21) into the carbon storage box (1) through the carbon dioxide injection hole (11), while the original seawater in the carbon storage box (1) is discharged from the drainage hole (12) on the side; When the liquid carbon dioxide injected into the carbon storage tank (1) reaches a critical value of the total amount of liquid carbon dioxide injected, a portion of the seawater is left behind, the unloading valve is closed, and the flow of liquid carbon dioxide into the carbon dioxide injection pipeline (21) is stopped; Step S5: close the switch valve on the carbon dioxide injection hole (11), dismantle the connection between the carbon dioxide liquid outlet of the carbon 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.

7. The method for storing subsea liquid carbon dioxide according to claim 6, characterized in that: When the unloading valve is opened, the liquid carbon dioxide in the carbon injection facility (2) is discharged from the carbon dioxide liquid outlet; when the unloading valve is closed, the discharge of liquid carbon dioxide to the carbon dioxide injection pipeline (21) is stopped.

8. The method for storing subsea liquid carbon dioxide according to claim 6, characterized in that: In step S1, the carbon dioxide injection hole (11) is kept open, so that seawater spontaneously flows into the carbon storage box (1) from the side drainage hole (12), and at the same time, the carbon storage box 1 as a whole gradually sinks and finally the inner cavity of the carbon storage box (1) is filled with seawater.

9. The method for storing subsea liquid carbon dioxide according to claim 6, characterized in that: The depth range of the seabed storage area is between 400-3000 meters below the sea surface.

10. The method for storing subsea liquid carbon dioxide according to claim 6, characterized in that: In step S4, when the carbon storage box (1) sinks to the seabed and approaches the seabed sediment, the injection of liquid carbon dioxide from the carbon dioxide injection hole (11) is continued, and the volume change rate of the liquid carbon dioxide injection is equal to the volume change rate of the original seawater in the carbon storage box (1) discharged from the side drainage hole (12).

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