Device and method for evaluating characteristics of seabed multi-phase sealed carbon dioxide

Abstract

The invention belongs to the technical field of ocean carbon dioxide sequestration, and discloses a seabed multiphase sequestration carbon dioxide characteristic evaluation device and method.The device comprises a test box, a support is installed in the test box, a reaction kettle is installed on the support, the reaction kettle comprises a sapphire tube, a top plate and a bottom plate, and the top plate and the bottom plate are installed at the two ends of the sapphire tube; a magnetic stirring rotor is arranged in the sapphire tube; a plurality of seawater inlets and outlets are formed in the top plate; a carbon dioxide injection opening is formed in the bottom plate; the motor is mounted on the bracket, and the motor is electrically connected with the magnetic stirring rotor; the carbon dioxide storage unit penetrates through the carbon dioxide injection port through a pipeline and is communicated with the sapphire tube; and the seawater container penetrates through the seawater inlet and outlet through a pipeline and is communicated with the sapphire tube. According to the technical scheme, the stability of CO2 in different phase states can be evaluated.

Description

Technical Field

[0001] The present invention belongs to the technical field of marine carbon dioxide storage, and in particular relates to a device and method for evaluating characteristics of seabed multiphase carbon dioxide storage. Background Art

[0002] CO 2 Excessive emissions are one of the main causes of the greenhouse effect, and carbon dioxide emissions are increasing every year, making the problem of global warming more serious. According to statistics, by the end of 2019, China's total greenhouse gas emissions accounted for 27% of the world's total. Finding feasible emission reduction solutions and achieving low-carbon development goals is not only in line with the world's development requirements, but also a strategic goal of protecting the ecological environment and achieving sustainable development.

[0003] Currently, CO 2 Storage methods mainly include geological storage, mineral storage, and ocean storage. 2 Compared with the previous two methods, storage has the characteristics of large storage space, easy operation, and low cost, and has greater application prospects. 2 There are two main methods of storage injection: indirect method (fertilization) and direct injection method. The indirect method is to fertilize the ocean to provide nutrients required by marine plants and promote their photosynthesis to consume CO. 2 , because adding nutrients will lead to unbalanced biological growth, which is more likely to cause other ecological problems and cannot be used for a long time; the direct injection method is to capture CO2 from the atmosphere. 2 Injection into the seabed, using liquid CO in the deep seabed 2 The density of liquid CO is greater than that of seawater. 2 The seabed sinks steadily, and on this basis, the low temperature and high pressure environment of the seabed is used to make CO 2 Further generation of hydrate solids will have a more significant effect on the stable storage. 2 The density is significantly lower than that of seawater. Only when a certain pressure is reached can liquid CO 2 The density of CO is greater than that of seawater. 2 There are requirements for the injection depth in the ocean, but the specific depth is not yet reported; on this basis, CO 2 There are also few reports on the state characteristics of hydrates in seawater.

[0004] In short, different phases (gas, liquid, solid) of CO 2 The actual state and characteristics of CO in the marine environment (which varies with depth) are still unclear, which will affect the storage of CO in the ocean. 2 Implementation and performance evaluation of the method. 2 The devices are usually blind reactors, which cannot effectively observe liquid CO2 , CO 2 The sinking and floating relationship between hydrate solids and seabed sediments; the visual evaluation observation system has the defect of low pressure (basically less than 15MPa); in addition, the existing device design is not comprehensive, lacking seawater flow and other parameters for different phases of CO 2 The stability of the impact of the evaluation function. Summary of the invention

[0005] The purpose of the present invention is to provide a device and method for evaluating characteristics of submarine multiphase carbon dioxide storage to solve the problems existing in the above-mentioned prior art.

[0006] On the one hand, in order to achieve the above-mentioned purpose, the present invention provides a device for evaluating characteristics of multi-phase storage of carbon dioxide on the seafloor, comprising:

[0007] A test box, wherein a bracket is installed in the test box, a reactor is rotatably installed on the bracket, the reactor comprises a sapphire tube and a top plate and a bottom plate installed at both ends of the sapphire tube, a magnetic stirring rotor is arranged in the sapphire tube; a plurality of seawater inlets and outlets are opened on the top plate, and a carbon dioxide injection port is opened on the bottom plate;

[0008] A motor is mounted on the bracket, and the motor is electrically connected to the magnetic stirring rotor;

[0009] a carbon dioxide storage unit, the carbon dioxide storage unit being connected to the sapphire tube through a pipeline passing through the carbon dioxide injection port;

[0010] A seawater container is connected to the sapphire tube through a pipeline passing through the seawater inlet and outlet.

[0011] Optionally, one end of the motor is electrically connected to the magnetic stirring rotor through a connecting line passing through the bottom plate, and the other end of the motor is electrically connected to an intelligent speed control system through a connecting line.

[0012] Optionally, the seawater container is also electrically connected to a constant speed and constant pressure displacement pump.

[0013] Optionally, sealing rings are provided at the contact points between the two ends of the sapphire tube and the top plate and the bottom plate.

[0014] Optionally, a movable piston is also provided in the sapphire tube.

[0015] On the other hand, to achieve the above-mentioned purpose, the present invention provides a method for evaluating characteristics of multi-phase carbon dioxide stored on the seafloor, which is applied to a device for evaluating characteristics of multi-phase carbon dioxide stored on the seafloor, comprising:

[0016] Step S1: injecting seawater into the sapphire tube, setting the temperature, and adjusting the seawater pressure in the sapphire tube and the pressure of the carbon dioxide storage unit based on first preset pressure data; injecting liquid carbon dioxide into the sapphire tube, and gradually pressurizing the seawater based on preset gradient data during the injection of the liquid carbon dioxide, to obtain suspension stable pressure data at which the liquid carbon dioxide can be stably suspended in the seawater and begin to sink;

[0017] Step S2: evaluating the dispersion characteristics of the liquid carbon dioxide by adjusting the spatial position of the sapphire tube in combination with the suspension stable pressure data, wherein the dispersion characteristics include longitudinal dispersion characteristics and transverse dispersion characteristics;

[0018] Step S3: installing a piston in the sapphire tube, injecting seawater and carbon dioxide into the sapphire tube to prepare solid carbon dioxide hydrate after the piston is installed, and dispersing the solid carbon dioxide hydrate in the seawater by a magnetic stirring rotor, adjusting the pressure of the sapphire tube to determine the sedimentation pressure of the solid carbon dioxide hydrate in the seawater;

[0019] Step S4: evaluating the stability characteristics of the carbon dioxide hydrate solid on the seabed based on the sedimentation pressure.

[0020] Optionally, the evaluation process of the longitudinal emission characteristics includes:

[0021] Continuously injecting seawater into the vertically placed sapphire tube until a second preset pressure data is reached, wherein the second preset pressure data is greater than the suspension stable pressure data;

[0022] After the temperature is stabilized, carbon dioxide is injected into the bottom of the sapphire tube, the time data of the carbon dioxide diffusing to the top of the sapphire tube is recorded, and the first longitudinal diffusion characteristic of the carbon dioxide is calculated based on the recorded time data and the height of the sapphire tube;

[0023] The sapphire tube is made to continuously inject seawater and continuously flow out seawater to construct an up-and-down flow environment of seawater, carbon dioxide is injected into the up-and-down flow environment of seawater, and the second longitudinal diffusion characteristic of carbon dioxide is calculated.

[0024] Optionally, the evaluation process of the lateral dispersion characteristics includes:

[0025] Continuously injecting seawater into the vertically placed sapphire tube until a second preset pressure data is reached, wherein the second preset pressure data is greater than the suspension stable pressure data;

[0026] After the temperature is stabilized, carbon dioxide is injected into the sapphire tube, and after the injection, the sapphire tube is turned to a horizontal direction, and the diffusion time of carbon dioxide from one end to the other end in the sapphire tube is monitored, and the first lateral diffusion characteristic of carbon dioxide is calculated based on the monitored diffusion time and the length of the sapphire tube;

[0027] Under constant pressure, seawater is injected into the upper part of one end of a horizontally placed sapphire tube, and seawater is discharged from the upper part of the other end to construct a seawater horizontal flow environment. Carbon dioxide is injected into the seawater horizontal flow environment, and the second lateral escape characteristic of carbon dioxide is calculated.

[0028] Optionally, the sapphire tube is pressure adjusted to determine the sedimentation pressure of carbon dioxide hydrate solids in seawater, specifically including:

[0029] The vertically placed sapphire tube is subjected to pressure regulation by first increasing the pressure and then decreasing the pressure, and the sedimentation pressure of the solid particles of carbon dioxide hydrate dispersed in the seawater is determined during the pressure regulation process.

[0030] Optionally, the step S4 specifically includes:

[0031] Assessing the stability characteristics of solid CO2 hydrate in the seafloor surface:

[0032] Injecting a fixed amount of seawater into the sapphire tube until a third preset pressure data is reached, wherein the third preset pressure data is greater than the sedimentation pressure;

[0033] After the temperature is stabilized, a fixed amount of liquid carbon dioxide is injected, stirring is started, and a seafloor surface environment is constructed. In the seafloor surface environment, the sapphire tube is continuously injected with seawater and continuously flows out seawater to construct a first type of ocean current environment;

[0034] Observe the change of the height of solid carbon dioxide hydrate over time in the first type of ocean current environment to obtain the stability and decomposition characteristics of solid carbon dioxide hydrate on the seafloor surface;

[0035] Assessing the stability characteristics of CO2 hydrate solids in shallow seafloor layers:

[0036] A quantitative amount of wet sediment is added into the sapphire tube after the piston is removed, and carbon dioxide is injected after the temperature is stabilized to convert the water in the wet sediment into solid carbon dioxide hydrate;

[0037] Injecting seawater into the sapphire tube based on the third preset pressure data to construct a shallow seabed environment, and observing static stability characteristics of carbon dioxide hydrate solids on the seabed surface in the shallow seabed environment;

[0038] The sapphire tube is made to continuously inject seawater and continuously discharge seawater to construct a second type of ocean current environment; the amount of carbon dioxide flashed out from the discharged seawater is collected in the second type of ocean current environment, and the decomposition characteristics of carbon dioxide hydrate solids in wet sediments are calculated based on the amount of flashed carbon dioxide.

[0039] The technical effects of the present invention are:

[0040] The present invention provides

[0041] The device established by the present invention is resistant to low temperature, high pressure, visible and rotatable. Combined with the established method, it can comprehensively evaluate the liquid and solid storage of CO2 in the seabed surface and shallow layers. 2 It can also simulate the ocean flow environment and analyze the effect of ocean currents on CO 2 The experimental environment can truly reflect the ocean flow environment, and the test data is authentic and reliable, with strong practicality, which has great significance for the storage of CO in the ocean. 2 Program formulation plays an important guiding role and can effectively guide practical applications on site. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0043] The drawings constituting a part of the present application are used to provide a further understanding of the present application. The illustrative embodiments and descriptions of the present application are used to explain the present application and do not constitute an improper limitation on the present application. In the drawings:

[0044] Figure 1 To evaluate the seafloor CO storage in the embodiment of the present invention 2 Schematic diagram of the stability device;

[0045] Explanation of the reference numbers: 1. Sapphire reactor; 2. Piston; 3. Sapphire tube; 4. Sealing ring; 5. Seawater injection port; 6. Discharge port; 7. Connecting screw; 8. Bracket; 9. Magnetic stirring rotor; 10. Motor; 11. Carbon dioxide injection port, 12. CO 2 Storage tank; 13. Intelligent speed control system; 14. Constant speed and constant pressure displacement pump; 15. Intermediate container; 16. Internal pipe line; 17. High and low temperature test chamber. DETAILED DESCRIPTION

[0046] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but should be understood as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0047] It should be understood that the terms described in the present invention are only for describing special embodiments and are not intended to limit the present invention. In addition, for the numerical range in the present invention, it should be understood that each intermediate value between the upper and lower limits of the scope is also specifically disclosed. Each smaller range between the intermediate value in any stated value or stated range and any other stated value or intermediate value in the described range is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded in the scope.

[0048] Unless otherwise indicated, all technical and scientific terms used herein have the same meanings as those of ordinary skill in the art generally understood by the present invention. Although the present invention describes only preferred methods, any method similar or equivalent to that described herein may also be used in the implementation or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods related to the documents. In the event of a conflict with any incorporated document, the content of this specification shall prevail.

[0049] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments of the present invention description without departing from the scope or spirit of the present invention. Other embodiments derived from the present invention description will be apparent to those skilled in the art. The present application description and examples are exemplary only.

[0050] The words “include,” “including,” “have,” “contain,” etc. used in this article are open-ended terms, meaning including but not limited to.

[0051] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present application will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0052] Embodiment 1

[0053] like Figure 1 As shown, in this embodiment, a device for evaluating characteristics of multi-phase storage of carbon dioxide on the seafloor is provided, comprising:

[0054] A test box, wherein a bracket 8 is installed in the test box, a reactor is rotatably installed on the bracket 8, the reactor comprises a sapphire tube 3 and a top plate and a bottom plate installed at both ends of the sapphire tube 3, a magnetic stirring rotor 9 is arranged in the sapphire tube 3; a plurality of seawater inlets and outlets are opened on the top plate, and a carbon dioxide injection port is opened on the bottom plate;

[0055] A motor 10 is mounted on the bracket 8, and the motor 10 is electrically connected to the magnetic stirring rotor 9;

[0056] A carbon dioxide storage unit, the carbon dioxide storage unit is connected to the sapphire tube 3 through a pipeline passing through the carbon dioxide injection port;

[0057] A seawater container is connected to the sapphire tube 3 through a pipeline passing through the seawater inlet and outlet.

[0058] A method for evaluating characteristics of multi-phase carbon dioxide stored on the seafloor, applied to a device for evaluating characteristics of multi-phase carbon dioxide stored on the seafloor, comprising:

[0059] Step S1: injecting seawater into the sapphire tube 3, setting the temperature, and adjusting the seawater pressure in the sapphire tube 3 and the pressure of the carbon dioxide storage unit based on the first preset pressure data; injecting liquid carbon dioxide into the sapphire tube 3, and gradually pressurizing the seawater based on the preset gradient data during the injection of the liquid carbon dioxide, to obtain the suspension stable pressure data at which the liquid carbon dioxide can be stably suspended in the seawater and begin to sink;

[0060] Step S2: evaluating the dispersion characteristics of the liquid carbon dioxide by adjusting the spatial position of the sapphire tube 3 in combination with the suspension stable pressure data, wherein the dispersion characteristics include longitudinal dispersion characteristics and transverse dispersion characteristics;

[0061] Step S3: installing the piston 2 in the sapphire tube 3, injecting seawater and carbon dioxide into the sapphire tube 3 to prepare solid carbon dioxide hydrate after the piston 2 is installed, and dispersing the solid carbon dioxide hydrate in the seawater through the magnetic stirring rotor 9, adjusting the pressure of the sapphire tube 3, and determining the sedimentation pressure of the solid carbon dioxide hydrate in the seawater;

[0062] Step S4: evaluating the stability characteristics of the carbon dioxide hydrate solid on the seabed based on the sedimentation pressure.

[0063] The purpose of this embodiment is to provide a method for evaluating the multi-phase storage of CO in the seafloor surface and shallow layer. 2 The device is resistant to low temperature and high pressure and can visually observe CO under different environments. 2 The device can be used to simulate the state of CO 2 Liquid CO injected into seawater 2 Effects of sinking and floating characteristics, diffusion characteristics, and seawater movement on CO 2 Carrying characteristics, CO 2 Hydrate solid sinking and floating characteristics, etc. 2 The formulation of the implementation plan of the method has important guiding significance and broad application prospects.

[0064] This embodiment provides a method for evaluating the storage of CO2 in the seafloor surface 2The experimental device for stability includes a high-pressure resistant sapphire tube 3, a frame 8 for fixing the sapphire tube 3, and a control system 13 (for controlling the stirring speed). A motor 10 is installed at one end of the frame, and the motor 10 can drive a magnetic stirring rotor 9 to provide stirring for the fluid in the sapphire tube 3. An end cap is provided at the other end, and a fluid injection port and an outlet 6 are provided on the end cap. The end cap and the motor end are connected by four detachable screws 7, and the sapphire tube 3 is installed in the middle of the four screws. The contact part between the sapphire tube 3 and the frame at both ends is provided with two sealing rings 4 of different diameters, which are used to seal the fluid in the sapphire tube 3 under high pressure, and at the same time, a buffer is applied between the contact surface of the sapphire tube 3 and the frame. A movable piston 2 is arranged in the sapphire tube 3, and the kettle body carrying the sapphire tube 3 can be rotated and fixed at any angle.

[0065] 1. Evaluation of liquid CO 2 Initial sinking pressure in sea water:

[0066] (1) Use a constant speed and constant pressure displacement pump 14 to fill the seawater in the intermediate container 15 into the sapphire tube 3 (without the piston 2, placed vertically), and increase the pressure to a given pressure P 0 , set the experimental temperature through the high and low temperature test box 17; at the same time, 2 (Sudan Red was added in advance) The pressure in tank 12 also increases to P 0 ;

[0067] (2) After the temperature and pressure are stable, a small amount of liquid CO is injected from the injection port 11 at the bottom of the sapphire tube 3 under constant pressure. 2 , if CO 2 The continuous buoyancy indicates that liquid CO 2 Density is less than that of seawater;

[0068] (3) Initial pressure of pressurized seawater P 0 , then proceed to step (2) to find the liquid CO 2 The stable suspension pressure in seawater provides a basis for the storage of CO2 in the seabed liquid state. 2 The site selection depth provides a basis for calculation.

[0069] 2. Evaluation of the method of storing CO2 in liquid form on the seafloor 2 Post-CO 2 -Seawater vertical dispersion characteristics:

[0070] (1) Use a constant speed and constant pressure displacement pump 14 to fill the seawater in the intermediate container 15 into the sapphire tube 3 (without the piston 2, placed vertically), and continue to inject until the experimental set pressure P 1 (This pressure is greater than that of liquid CO in seawater 2 Suspension stability pressure P 0 );

[0071] (2) A certain amount of liquid CO pre-added with Sudan red is injected at a constant pressure from the injection port 11 at the lower end of the sapphire tube 3. 2 , looking at liquid CO in static state 2 Is it diffused upward in seawater? If so, record CO 2 The time it takes to diffuse to the top of the sapphire tube 3 is used to calculate the apparent diffusion velocity (height of the sapphire tube 3 / migration time);

[0072] (3) For environments with up and down currents, a pipeline can be further connected from the injection port of the top end cap to the sapphire tube 3, with the outlet of the pipeline slightly higher than the liquid CO 2 On the surface, seawater is continuously injected from the pipeline and discharged from another outlet 6 on the top end cover to create an environment where seawater flows up and down, and to grasp the liquid CO under the action of the up and down flow of seawater. 2 The time it takes to diffuse from the bottom to the top is used to calculate the apparent diffusion rate, and the influence of seawater flow rate can be further analyzed.

[0073] 3. Evaluation of the method of storing CO2 in a liquid state on the seafloor 2 Post-CO 2 - Characteristics of lateral dispersion of seawater:

[0074] (1) Use a constant speed and constant pressure displacement pump 14 to fill the seawater in the intermediate container 15 into the sapphire tube 3 (without the piston 2, placed vertically) and continue to inject until the experimental set pressure P 1 (This pressure is greater than that of liquid CO in seawater 2 Suspension stability pressure P 0 );

[0075] (2) A certain amount of liquid CO pre-added with Sudan red is injected at a constant pressure from the injection port 11 at the bottom of the sapphire tube 3. 2 (Note CO 2 During the process, seawater is slowly discharged from the top of the sapphire tube 3 to maintain a constant pressure. After the injection, the device is turned horizontally and the CO 2 Lateral diffusion characteristics in seawater to monitor CO 2 The time it takes to diffuse from one end to the other end of the sapphire tube 3 is used to calculate the apparent diffusion velocity and compare it with the longitudinal diffusion velocity;

[0076] (3) For areas with horizontal ocean currents, after injecting fluid (seawater, liquid CO 2 ) and then turn the sapphire tube 3 to a horizontal position (the end cap with the fluid injection port is at the top). By using the density difference, the upper layer in the horizontal tube is seawater and the lower layer is liquid CO 2 Then, seawater is injected from the injection port of the sapphire tube 3, and seawater is discharged from the injection port 11 at the other end (under constant pressure) to create a seawater horizontal flow environment. The experimental process determines the liquid CO 2The change of height over time can help us understand the effect of seawater horizontal flow on CO 2 carryover effect.

[0077] 4. Evaluation of CO in seawater 2 Hydrate solid sedimentation pressure:

[0078] (1) A certain amount of seawater is injected from the injection port 11 of the sapphire tube 3 (equipped with a piston 2) using a constant speed and constant pressure displacement pump 14 (the kettle is vertical, with the end with the stirring system 9 at the bottom), and the experimental temperature is set;

[0079] (2) After the temperature stabilizes, inject a certain amount of CO from injection port 11. 2 (4-5MPa) synthesizes some CO in the surface of seawater 2 Hydrate solid, start stirring system 9 to allow CO 2 Hydrate particles are dispersed in seawater;

[0080] (3) Then connect the high-pressure pipeline at the injection port 6 to pressurize the sapphire tube 3 at 1 MPa / h. Stabilize at each pressure for a period of time (not less than 10 minutes) to determine the dispersed CO in the seawater. 2 Hydrate solid particles begin to sink pressure P 2 ;

[0081] (4) Then P 2 As the starting point, the pressure was gradually reduced by 0.1 MPa / h, and each pressure was kept stable for a period of time (not less than 10 minutes). 2 Further precise quantification was performed.

[0082] 5. Evaluation of the hydrate method for storing CO2 in the seafloor surface 2 Post-CO 2 Hydrate stability characteristics:

[0083] (1) Add a certain amount of seawater into the sapphire tube 3 and continue to pressurize it to a set pressure (higher than CO 2 The sedimentation pressure of hydrate in seawater is P2), and the experimental temperature is set;

[0084] (2) After the temperature stabilizes, inject a certain amount of liquid CO from the injection port 11. 2 , start the stirring system 9, and convert about half of the seawater into CO 2 Hydrate solids, building a seawater-CO 2 Hydrate solid coexistence environment, at this time CO 2 The hydrate solids settle in the lower part;

[0085] (3) Connect a pipeline from the injection port of the top end cover, and the outlet of the pipeline is slightly higher than the solid CO 2Hydrates are continuously injected with seawater from the pipeline and discharged from the top end cap 6 to create an ocean current-like environment and observe CO 2 The decrease of hydrate solid height over time can help us understand the changes of CO 2 Stability and decomposition characteristics of hydrate solids in seawater.

[0086] VI. Evaluation of shallow seafloor hydrate storage of CO 2 Post-CO 2 Hydrate solid stability characteristics:

[0087] (1) Add a certain amount of wet sediment (100% water) into the sapphire tube 3 (without the piston 2). After the temperature stabilizes, inject CO into the sapphire tube 3. 2 , converting water in the sediment into CO 2 Hydrate;

[0088] (2) Reduce the pressure in the sapphire tube 3 to the experimental temperature CO 2 About 0.3MPa above the hydrate phase equilibrium pressure;

[0089] (3) Connect a pipeline from the inside of the top cover at 5 to inject seawater to remove the gaseous CO 2 After replacement, a seawater-CO 2 In an environment where hydrate solids coexist, seawater is continuously injected to increase the pressure to simulate the shallow seabed pressure;

[0090] (4) First, look at CO statically 2 Hydrate solid stability (CO on the contact surface between sapphire tube 3 and sediment) 2 hydrate solid);

[0091] (5) For ocean current environments, a pipeline is connected from the top end cap 5 to inject seawater, and the seawater is discharged from another outlet 6 to collect the CO flashed out from the discharged seawater. 2 If there is no CO 2 Output, indicating that CO 2 Hydrate solids have good stability; if there is CO 2 Output, combined with the output, to calculate the CO in the sediment 2 Hydrate solid decomposition rate.

[0092] Liquid CO 2 Study on buoyancy and sinking pressure in seawater:

[0093] (1) Using a constant speed and constant pressure displacement pump 14, the seawater near the South China Sea Hippocampus cold spring in the intermediate container 15 is filled into the sapphire tube 3 (without the piston 2, placed vertically) (100 mL), and the pressure is increased to an initial given pressure of 10 MPa. The experimental temperature is set to 4°C (simulating the seabed temperature near the South China Sea Hippocampus cold spring) through the high and low temperature test box 17; at the same time, CO 2 (Sudan Red was added in advance) The pressure of storage tank 12 also increased to 10MPa;

[0094] (2) After the temperature and pressure are stable, inject about 1 mL of liquid CO from the injection port 11 at the bottom of the sapphire tube 3 under constant pressure. 2 , found that CO 2 It quickly floated to the top of the device, indicating that liquid CO 2 Density is less than the given density of seawater;

[0095] (3) Then, the seawater and liquid CO are pressurized with a pressure gradient of 1 MPa. 2 Initial pressure, then step (2) was performed, and it was found that at 27 MPa, liquid CO 2 Stable and not floating at the bottom of the sapphire tube 3;

[0096] (4) Then reduce the pressure gradient of seawater and liquid CO with a pressure gradient of 0.1 MPa. 2 The initial pressure of liquid CO was found to be 26.6 MPa. 2 The liquid CO at the bottom of the sapphire tube 3 is stable and does not float. 2 Slowly float up from the bottom of sapphire tube 3, and finally determine the liquid CO 2 The initial sinking pressure in the seawater near the South China Sea Hippocampus Cold Spring is 26.6 MPa, which means that in order to make liquid CO 2 To be able to stably seal and not float, the required pressure cannot be lower than 26.6MPa.

[0097] CO 2 Study on the sedimentation and buoyancy pressure of hydrate solids in seawater:

[0098] (1) 60 mL of seawater was injected from the injection port 11 of the sapphire tube 3 (equipped with a movable piston 2) using a constant speed and constant pressure displacement pump 14 (the kettle was vertical, with the end with the stirring system 9 at the bottom), and the seawater pressure was increased to 5 MPa. The experimental temperature was set to 4 °C (simulating the seabed temperature);

[0099] (2) After the temperature stabilizes, inject 5 mL of liquid CO from injection port 11. 2 (Injection at constant pressure of 5MPa), turn on the stirring system to synthesize some CO on the surface of seawater 2 Hydrate solid, CO generated by stirring system 9 2Hydrate particles are dispersed in the surface layer of seawater;

[0100] (3) Then, the high-pressure pipeline at the injection port 6 was connected to inject hydraulic oil into the sapphire tube 3, and the pressure at one end of the synthetic hydrate was increased at a rate of 1 MPa / min through the piston. Each pressure was stabilized for a period of time (10 minutes). It was found that when the pressure increased to 28 MPa, the CO floating on the seawater surface 2 Hydrate solid particles start;

[0101] (4) Starting from 28 MPa, the pressure was gradually reduced at a rate of 0.1 MPa / h. Each pressure was stabilized for a period of time (not less than 10 minutes). It was found that when the pressure dropped to 27.3 MPa, the CO precipitated at the bottom of the sapphire tube 3 2 Hydrate particles began to float up again, and finally the CO in seawater at 4°C was determined. 2 The initial sedimentation pressure of hydrate particles is 27.4 MPa.

[0102] The device established in this embodiment is resistant to low temperature, high pressure, visible and rotatable. Combined with the established method, it can comprehensively evaluate the liquid and solid storage of CO2 in the seafloor surface and shallow layers. 2 It can also simulate the ocean flow environment and analyze the effect of ocean currents on CO 2 The experimental environment can truly reflect the ocean flow environment, and the test data is authentic and reliable, with strong practicality, which has great significance for the storage of CO in the ocean. 2 Program formulation plays an important guiding role and can effectively guide practical applications on site.

[0103] The above is only a preferred specific implementation of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed in the present application should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

Claims

1. A device for evaluating characteristics of multi-phase storage of carbon dioxide on the seafloor, characterized in that: include: A test box, wherein a bracket (8) is installed in the test box, a reaction kettle is rotatably installed on the bracket (8), the reaction kettle comprises a sapphire tube (3) and a top plate and a bottom plate installed at both ends of the sapphire tube (3), a magnetic stirring rotor (9) is arranged in the sapphire tube (3); a plurality of seawater inlets and outlets are opened on the top plate, and a carbon dioxide injection port is opened on the bottom plate; A motor (10) is mounted on the bracket (8), and the motor (10) is electrically connected to the magnetic stirring rotor (9); a carbon dioxide storage unit, the carbon dioxide storage unit being connected to the sapphire tube (3) through a pipeline passing through the carbon dioxide injection port; A seawater container is connected to the sapphire tube (3) through a pipeline passing through the seawater inlet and outlet.

2. The device for evaluating characteristics of multi-phase storage of carbon dioxide on the seafloor according to claim 1, characterized in that: One end of the motor (10) is electrically connected to the magnetic stirring rotor (9) via a connecting wire passing through the bottom plate, and the other end is electrically connected to an intelligent speed regulation system (13) via a connecting wire.

3. The device for evaluating characteristics of seabed multiphase carbon dioxide storage according to claim 1, characterized in that: The seawater container is also electrically connected to a constant speed and constant pressure displacement pump (14).

4. The device for evaluating characteristics of multi-phase storage of carbon dioxide on the seafloor according to claim 1, characterized in that: Sealing rings (4) are provided at the contact points between the two ends of the sapphire tube (3) and the top plate and the bottom plate.

5. The device for evaluating characteristics of submarine multiphase carbon dioxide storage according to claim 1, characterized in that: A movable piston (2) is also provided in the sapphire tube (3).

6. A method for evaluating characteristics of multi-phase storage of carbon dioxide on the seafloor, applied to a device for evaluating characteristics of multi-phase storage of carbon dioxide on the seafloor as claimed in any one of claims 1 to 5, characterized in that: include: Step S1: injecting seawater into the sapphire tube (3), setting the temperature, and adjusting the seawater pressure in the sapphire tube (3) and the pressure of the carbon dioxide storage unit based on first preset pressure data; injecting liquid carbon dioxide into the sapphire tube (3), and gradually pressurizing the seawater based on preset gradient data during the injection of the liquid carbon dioxide, to obtain suspension stable pressure data at which the liquid carbon dioxide can be stably suspended in the seawater and begins to sink; Step S2: evaluating the dispersion characteristics of the liquid carbon dioxide by adjusting the spatial position of the sapphire tube (3) in combination with the suspension stable pressure data, wherein the dispersion characteristics include longitudinal dispersion characteristics and transverse dispersion characteristics; Step S3: installing a piston (2) in the sapphire tube (3), injecting seawater and carbon dioxide into the sapphire tube (3) after the piston (2) is installed to prepare solid carbon dioxide hydrate, and dispersing the solid carbon dioxide hydrate in the seawater by means of a magnetic stirring rotor (9), adjusting the pressure of the sapphire tube (3), and determining the sedimentation pressure of the solid carbon dioxide hydrate in the seawater; Step S4: evaluating the stability characteristics of the carbon dioxide hydrate solid on the seabed based on the sedimentation pressure.

7. A method for evaluating characteristics of submarine multiphase carbon dioxide storage according to claim 6, characterized in that: The evaluation process of the longitudinal emission characteristics includes: Continuously injecting seawater into a vertically placed sapphire tube (3) until a second preset pressure data is reached, wherein the second preset pressure data is greater than the suspension stability pressure data; After the temperature is stabilized, carbon dioxide is injected into the bottom of the sapphire tube (3), the time data of the carbon dioxide diffusing to the top of the sapphire tube (3) is recorded, and the first longitudinal diffusion characteristic of the carbon dioxide is calculated based on the recorded time data and the height of the sapphire tube (3); The sapphire tube (3) is made to continuously inject seawater and continuously flow out seawater to construct an up-and-down flow environment of seawater, carbon dioxide is injected into the up-and-down flow environment of seawater, and a second longitudinal diffusion characteristic of carbon dioxide is calculated.

8. A method for evaluating characteristics of seafloor multiphase carbon dioxide storage according to claim 6, characterized in that: The evaluation process of the lateral dispersion characteristics includes: Continuously injecting seawater into a vertically placed sapphire tube (3) until a second preset pressure data is reached, wherein the second preset pressure data is greater than the suspension stability pressure data; After the temperature is stabilized, carbon dioxide is injected into the sapphire tube (3), and after the injection, the sapphire tube (3) is turned to a horizontal direction, and the diffusion time of the carbon dioxide from one end to the other end in the sapphire tube (3) is monitored, and a first lateral diffusion characteristic of the carbon dioxide is calculated based on the monitored diffusion time combined with the length of the sapphire tube (3); Under constant pressure, seawater is injected into the upper part of one end of a horizontally placed sapphire tube (3), and seawater is discharged from the upper part of the other end, so as to construct a seawater horizontal flow environment. Carbon dioxide is injected into the seawater horizontal flow environment, and the second lateral escape characteristic of carbon dioxide is calculated.

9. A method for evaluating characteristics of submarine multiphase carbon dioxide storage according to claim 6, characterized in that: The sapphire tube (3) is pressure adjusted to determine the sedimentation pressure of carbon dioxide hydrate solids in seawater, specifically comprising: The vertically placed sapphire tube (3) is subjected to pressure regulation by first increasing the pressure and then decreasing the pressure, and the sedimentation pressure of the carbon dioxide hydrate solid particles dispersed in the seawater is determined during the pressure regulation process.

10. The method for evaluating characteristics of submarine multiphase carbon dioxide storage according to claim 6, characterized in that: The step S4 specifically includes: Assessing the stability characteristics of solid CO2 hydrate in the seafloor surface: Injecting a certain amount of seawater into the sapphire tube (3) until a third preset pressure data is reached, wherein the third preset pressure data is greater than the sedimentation pressure; After the temperature is stabilized, a certain amount of liquid carbon dioxide is injected, stirring is started, and a seafloor surface environment is constructed. In the seafloor surface environment, the sapphire tube (3) is continuously injected with seawater and continuously flows out seawater to construct a first type of ocean current environment; Observe the change of the height of solid carbon dioxide hydrate over time in the first type of ocean current environment to obtain the stability and decomposition characteristics of solid carbon dioxide hydrate on the seafloor surface; Assessing the stability characteristics of CO2 hydrate solids in shallow seafloor layers: A certain amount of wet sediment is added into the sapphire tube (3) after the piston (2) is removed, and carbon dioxide is injected after the temperature is stabilized, so that water in the wet sediment is converted into carbon dioxide hydrate solid; Injecting seawater into the sapphire tube (3) based on third preset pressure data to construct a shallow seabed environment, and observing static stability characteristics of carbon dioxide hydrate solids on the seabed surface in the shallow seabed environment; The sapphire tube (3) is made to continuously inject seawater and continuously discharge seawater to construct a second type of ocean current environment; the amount of carbon dioxide flashed out of the discharged seawater is collected in the second type of ocean current environment, and the decomposition characteristics of carbon dioxide hydrate solids in the wet sediment are calculated based on the amount of carbon dioxide flashed out.

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