A composite promoter for hydrate sequestration of carbon dioxide and its application

Abstract

The application relates to a composite promoter for hydrate storage of carbon dioxide and application thereof, which comprises a thermodynamic promoter tetrabutylammonium bromide TBAB, tetramethylammonium chloride TMAC and a surfactant octyl glucoside OGP, and after mixing with water, the mass percentage concentration of the three is TBAB: 0.001-40 wt%, TMAC: 0.1-50 wt% and OGP: 0.001-1 wt%. The application can promote the generation of CO2 hydrate, solves the problems of higher hydrate production pressure and slower reaction rate in the hydrate reaction, and makes the hydrate method for storing CO2 more valuable in industrial application.

Description

Technical Field

[0001] This application relates to a hydrate promoter, and more particularly to a composite promoter for carbon dioxide sequestration via hydrates and its application. Background Technology

[0002] In recent years, the "greenhouse effect" has become a hot social issue and a global environmental problem. CO2 is one of the main gases that cause the greenhouse effect. Combustion of coal produces a large amount of CO2, and if it is released directly, it will pollute the environment. Therefore, it needs to be stored.

[0003] The core of CO2 sequestration technology using hydrates is to capture and store CO2 by forming stable gaseous hydrates. However, the effect of a single surfactant on promoting hydrate growth is relatively limited, specifically due to the following drawbacks:

[0004] 1. Harsh thermodynamic conditions: This is mainly reflected in the high pressure required for hydrate production without thermodynamic promoters, resulting in high experimental costs and high energy consumption for industrialization.

[0005] 2. Hydrate Stability: Although studies have shown that CO2 exhibits high stability after forming hydrates, its long-term stability still requires further verification. Especially in practical applications of CO2 sequestration using hydrates, it is necessary to ensure the stability of CO2 hydrates over extended periods to prevent decomposition or leakage.

[0006] 3. The problem of slow conversion rate in the kinetic process: The slow gas-liquid diffusion mass transfer process will affect the kinetics of CO2 hydrate formation during the storage process.

[0007] For the reasons mentioned above, it is necessary to study a composite promoter that can overcome the limitations of the promoting effect of single surfactants on hydrate growth. Summary of the Invention

[0008] The purpose of this application is to provide a composite promoter for hydrated carbon dioxide sequestration that reduces the pressure required for the hydration reaction, improves the hydration reaction rate and the stability of the hydrate; based on the former purpose, another purpose of this application is to propose the application of the composite promoter.

[0009] This application is implemented as follows: a composite promoter for carbon dioxide hydrate sequestration, comprising the thermodynamic promoter tetrabutylammonium bromide (TBAB), tetramethylammonium chloride (TMAC), and the surfactant octyl glucoside (OGP), wherein the mass percentage concentrations of the three components after mixing with water are TBAB: 0.001-40wt%, TMAC: 0.1-50wt%, and OGP: 0.001-1wt%.

[0010] Furthermore, a formulation with a TBAB mass percentage concentration of 20 wt%, a TMAC mass percentage concentration of 5 wt%, and an OGP mass percentage concentration of 0.3 wt% was used. Under these conditions, the CO2 hydrate formation pressure was significantly reduced to 2.3 MPa, the induction time was shortened to 15 minutes, and the hydrate stability reached 75 hours. This formulation fully utilizes the thermodynamic complementarity of TMAC and TBAB, as well as the enhancing effect of OGP on reaction kinetics, demonstrating the fundamental advantages of the ternary system.

[0011] Furthermore, the TBAB mass percentage concentration was adjusted to 15 wt%, the TMAC mass percentage concentration to 8 wt%, and the OGP mass percentage concentration to 0.8 wt%. Under this ratio, the generation pressure was 2.5 MPa, but the induction time was further shortened to 10 minutes, indicating that the higher OGP concentration effectively accelerated the nucleation and growth process.

[0012] Furthermore, a formulation with 25 wt% TBAB, 15 wt% TMAC, and 0.1 wt% OGP was also used. This formulation focused on optimizing thermodynamic conditions, reducing the generation pressure to a low level of 2.0 MPa and the induction time to 20 minutes. This demonstrates that by adjusting the ratio of the two thermodynamic promoters, the generation pressure can be finely controlled to a certain extent.

[0013] Furthermore, the concentrations of TBAB, TMAC, and OGP were 18 wt%, 10 wt%, and 0.4 wt%, respectively. Under these conditions, the formation pressure was 2.4 MPa and the induction time was 16 minutes, but the hydrate stability was particularly outstanding, extending to over 90 hours. This indicates that through careful formulation, the ternary system can form CO2 hydrates with more complete structures and significantly enhanced stability.

[0014] An experimental apparatus for determining a composite accelerator includes a constant temperature device with an internal cavity. A high-pressure reactor for hydration reaction is housed within the constant temperature device. An observation window is provided on the surface of the high-pressure reactor. The internal cavity of the high-pressure reactor is connected to the lower part of a buffer tank located above the high-pressure reactor. A piston is installed inside the buffer tank. The cavity above the piston is connected to a hand-cranked pump via a pressurization pipe. The cavity below the piston is connected to the internal cavity of the high-pressure reactor via an inlet pipe. The cavity below the piston is connected to a parallel gas storage bottle and a vacuum pump via an inlet pipe. The upper part of the internal cavity of the high-pressure reactor is connected to an exhaust pipe, and the lower part is connected to inlet and outlet liquid pipes. A magnetic stirrer is installed at the bottom of the high-pressure reactor, with its stirring end extending into the internal cavity. A first pressure sensor is installed at the pressurization chamber of the hand-cranked pump. A second pressure sensor and a temperature sensor are installed within the constant temperature device. The first pressure sensor, the second pressure sensor, and the temperature sensor are connected to a data recording and display device circuitry located outside the constant temperature device.

[0015] The application of a composite promoter for carbon dioxide sequestration via hydrates includes the following steps:

[0016] S1. Inject the composite accelerator and experimental solution described in this application into the high-pressure reactor through the inlet and outlet liquid pipelines. Then close the control valve at the gas storage bottle, the control valve at the inlet and outlet liquid pipelines, and the control valve on the exhaust pipeline. Then turn on the vacuum pump to remove the gas from the high-pressure reactor and each pipeline. The vacuuming time is 30 minutes.

[0017] S2. Control the temperature of the thermostat to maintain a stable temperature inside the high-pressure reactor. Then, open the control valve at the gas storage bottle and close the control valve at the vacuum pump to introduce CO2 gas into the high-pressure reactor. Use a hand pump to pressurize the high-pressure reactor until the set pressure is reached, then stop the gas intake. When the temperature inside the high-pressure reactor drops to the set temperature, turn on the magnetic stirrer at the bottom of the high-pressure reactor and start timing. As CO2 hydrates are formed, the time required for visible CO2 hydrate crystal nuclei to appear in the observation window is the induction time of CO2 hydrates.

[0018] S3. Once the temperature and pressure in the high-pressure reactor remain constant, it can be considered that CO2 hydrate has been completely generated. Open the control valve on the exhaust pipe and control the exhaust speed (pressure drops by 0.01 MPa every 5-7 seconds) to maintain a constant temperature inside the high-pressure reactor. Transmit the temperature and pressure data to the data recording and display device through the temperature sensor, the first pressure sensor, and the second pressure sensor to record the temperature and pressure values ​​of CO2 hydrate during the decomposition process. Find the equilibrium point for CO2 hydrate sequestration by observing the observation window.

[0019] S4. After opening the exhaust valve, the hydrate begins to decompose. When a bright spot appears in the observation window, record the phase equilibrium data at this time, which is the equilibrium point of CO2 sequestration by the hydrate method.

[0020] Furthermore, in step S2, the temperature inside the high-pressure reactor is 2℃~10℃, the specific pressure is 3~5 MPa, and the magnetic stirrer inside the high-pressure reactor rotates at 500 rpm.

[0021] By implementing the above technical solution, this application combines TBAB, TMAC, and OGP in a certain ratio to form a composite promoter. TBAB can significantly reduce the pressure required for CO2 to form hydrates. TBAB can participate in hydrate formation because it can fill the pores in the hydrate structure during the hydrate formation process, increasing the pore filling rate and promoting hydrate stability. OGP can increase the reaction rate of the hydration reaction. By introducing TMAC, its smaller molecular size may have a complementary effect with TBAB, potentially leading to a denser and more complete hydrate crystal structure. TMAC has the characteristics of smaller molecular weight and higher solubility in water, and it exhibits a unique thermodynamic promoting effect under different temperature and pressure conditions. The addition of TMAC can change the phase equilibrium conditions of hydrates, allowing them to form under milder conditions, which is of great significance for reducing energy consumption and operational difficulty in the storage process. This invention verifies the potential of composite promoters to improve the short- to medium-term stability of hydrates by comparing the stability maintenance time of hydrates under experimental conditions. It further clarifies that this application can promote the formation of CO2 hydrates, solving the problems of high production pressure and slow reaction rate in hydrate reaction, and making the hydrate method for CO2 sequestration more valuable for industrial applications. Attached Figure Description

[0022] The specific structure of this application is given by the following figures and embodiments:

[0023] Figure 1 This is a schematic diagram of the experimental apparatus of this application.

[0024] Legend: 1. Gas storage cylinder, 2. Vacuum pump, 3. Inlet pipe, 4. Piston, 5. Buffer tank, 6. Thermostat, 7. Exhaust pipe, 8. First pressure sensor, 9. Hand pump, 10. Pressurization pipe, 11. Inlet and outlet pipes, 12. High-pressure reactor, 13. Magnetic stirrer, 14. Observation window, 15. Temperature sensor, 16. Second pressure sensor. Detailed Implementation

[0025] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0026] In the description of this application, it should be understood that the terms "center", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.

[0027] Example: A composite promoter for carbon dioxide hydrate sequestration includes the thermodynamic promoter tetrabutylammonium bromide (TBAB), tetramethylammonium chloride (TMAC), and the surfactant octyl glucoside (OGP). The mass percentage concentrations of the three components after mixing with water are TBAB: 0.001-40wt%, TMAC: 0.1-50wt%, and OGP: 0.001-1wt%.

[0028] Furthermore, the concentrations of TBAB (20 wt%), TMAC (5 wt%), and OGP (0.3 wt%) were determined. Under these conditions, the CO2 hydrate formation pressure was significantly reduced to 2.3 MPa, the induction time was shortened to 15 minutes, and the hydrate stability reached 75 hours. This formulation fully utilizes the thermodynamic complementarity of TMAC and TBAB, as well as the enhancing effect of OGP on reaction kinetics, demonstrating the fundamental advantages of the ternary system.

[0029] Furthermore, the TBAB mass percentage concentration was adjusted to 15 wt%, the TMAC mass percentage concentration to 8 wt%, and the OGP mass percentage concentration to 0.8 wt%. Under this ratio, the generation pressure was 2.5 MPa, but the induction time was further shortened to 10 minutes, indicating that the higher OGP concentration effectively accelerated the nucleation and growth process.

[0030] Furthermore, the concentrations of TBAB, TMAC, and OGP were 25 wt%, 15 wt%, and 0.1 wt%, respectively. This formulation focused on optimizing thermodynamic conditions, reducing the generation pressure to a low level of 2.0 MPa and the induction time to 20 minutes. This demonstrates that by adjusting the ratio of the two thermodynamic promoters, the generation pressure can be finely controlled to a certain extent.

[0031] Furthermore, the concentrations of TBAB, TMAC, and OGP were 18 wt%, 10 wt%, and 0.4 wt%, respectively. Under these conditions, the formation pressure was 2.4 MPa and the induction time was 16 minutes, but the hydrate stability was particularly outstanding, extending to over 90 hours. This indicates that through careful formulation, the ternary system can form CO2 hydrates with more complete structures and significantly enhanced stability.

[0032] like Figure 1 As shown, an experimental apparatus for determining a composite accelerator includes a constant temperature device 6 with an internal cavity. A high-pressure reactor 12 for hydration reaction is installed inside the constant temperature device 6. An observation window 14 is provided on the surface of the high-pressure reactor 12. The internal cavity of the high-pressure reactor 12 is connected to the lower part of a buffer tank 5 located on the upper side of the high-pressure reactor 12. A piston 4 is installed inside the buffer tank 5. The cavity above the piston 4 is connected to a hand-cranked pump 9 through a pressurization pipe 10. The cavity below the piston 4 is connected to the internal cavity of the high-pressure reactor 12. The cavity below the piston 4 is connected to a parallel gas storage bottle 1 and a vacuum pump 2 through an air inlet pipe 3. The upper part of the internal cavity of the high-pressure reactor 12 is connected to an exhaust pipe 7. The lower part of the internal cavity of the high-pressure reactor 12 is connected to an inlet / outlet liquid pipe 11.

[0033] Furthermore, a magnetic stirrer 13 is provided at the bottom of the high-pressure reactor 12, with the stirring end of the magnetic stirrer 13 extending into the inner cavity of the high-pressure reactor 12. The magnetic stirrer 13 is used to uniformly mix the gas and liquid phases and enhance mass transfer within the reactor. Its speed is adjustable, which is existing technology and not the point of this invention. Therefore, its specific structure will not be described in detail.

[0034] Furthermore, the constant temperature device 6 is existing technology and is not the point of invention of this application. Its specific structure will not be described in detail. It is equipped with a second pressure sensor 16 and a temperature sensor 15. The second pressure sensor 16 and the temperature sensor 15 are connected to the data recording and display device circuit located outside the constant temperature device 6.

[0035] Furthermore, a first pressure sensor 8 is provided at the pressurization chamber of the hand pump 9, and the first pressure sensor 8 is connected to the data recording and display device circuit located outside the constant temperature device 6.

[0036] The data recording and display device is used to record pressure and temperature data transmitted through the first pressure sensor 8, the second pressure sensor 16 and the temperature sensor 15. This is also prior art and not the point of invention of this application. The specific structure is not described in detail.

[0037] Furthermore, control valves are installed on the air inlet pipe 3, the exhaust pipe 7, the liquid inlet / outlet pipe 11, and at the connection points between the air inlet pipe 3 and the gas storage cylinder 1 and the vacuum pump 2.

[0038] The application of a composite promoter for carbon dioxide sequestration via hydrates includes the following steps:

[0039] S1. Inject the composite accelerator and experimental solution described in this application into the high-pressure reactor 12 through the inlet / outlet liquid pipeline 11. Then close the control valve at the gas storage bottle 1, the control valve at the inlet / outlet liquid pipeline 11, and the control valve on the exhaust pipeline 7. Then turn on the vacuum pump 2 to remove the gas from the high-pressure reactor 12 and each pipeline. The vacuuming time is 30 minutes.

[0040] S2. Control the temperature of the thermostat 6 to maintain a stable temperature inside the high-pressure reactor 12. Then, open the control valve at the gas storage bottle 1 and close the control valve at the vacuum pump 2 to introduce CO2 gas into the high-pressure reactor 12. Use the hand pump 9 to pressurize the high-pressure reactor 12. Stop the gas intake after reaching the set pressure. When the temperature inside the high-pressure reactor 12 drops to the set temperature, turn on the magnetic stirrer 13 below the high-pressure reactor 12 and start timing. As CO2 hydrates are generated, the time required for visible CO2 hydrate crystal nuclei to appear in the observation window 14 is the induction time of CO2 hydrates.

[0041] S3. Once the temperature and pressure in the high-pressure reactor 12 remain constant, it can be considered that CO2 hydrate has been completely generated. Open the control valve on the exhaust pipe 7 to control the exhaust speed (pressure drops by 0.01 MPa every 5-7 seconds) and keep the temperature inside the high-pressure reactor 12 constant. Transmit the temperature and pressure data to the data recording and display device through the temperature sensor 15, the first pressure sensor 8, and the second pressure sensor 16 to record the temperature and pressure values ​​of CO2 hydrate during the decomposition process. Find the equilibrium point for CO2 hydrate sequestration by observing the observation window 14.

[0042] S4. After opening the exhaust valve, the hydrate begins to decompose. When a bright spot appears in observation window 14, record the phase equilibrium data at this time, which is the equilibrium point of CO2 sequestration by the hydrate method.

[0043] Furthermore, the experimental solution refers to a mixture of one or more of the following components: deionized water, NaCl, calcium chloride, sodium sulfate, etc.

[0044] Furthermore, in step S2, the temperature inside the high-pressure reactor 12 is 2℃~10℃, the specific pressure is 3~5Mpa, and the magnetic stirrer 13 operates at a speed of 500 rpm.

[0045] Further, in step S1, the reactor is cleaned: the control valves at vacuum pump 2 and inlet pipe 3 are opened, the control valves at inlet / outlet liquid pipe 11 and exhaust pipe 7 are closed, vacuum pump 2 is started to evacuate the high-pressure reactor 12, and then the control valves at vacuum pump 2 and inlet pipe 3 are closed, and the control valves at inlet / outlet liquid pipe 11 are opened to draw in 80... Add ml of deionized water and turn on the magnetic stirrer 13 to clean the high-pressure reactor 12 3-4 times. The cleaned deionized water is discharged from the inlet / outlet pipe 11. Then, open the control valves at the vacuum pump 2 and the air inlet pipe 3 again, close the control valves at the inlet / outlet pipe 11, use the vacuum pump 2 to evacuate the high-pressure reactor 12, close the control valves at the vacuum pump 2 and the air inlet pipe 3, open the control valves at the inlet / outlet pipe 11 to draw in the composite accelerator described in this application and rinse 1-2 times. The rinsed composite accelerator is discharged from the inlet / outlet pipe 11. Finally, inject 50 ml of the composite accelerator and experimental solution described in this application into the high-pressure reactor 12 at a volume ratio of 1:25.

[0046] Furthermore, in step S2, the gas is introduced: the experimental gas (CO2) is introduced from the gas storage bottle 1 into the high-pressure reactor 12, and each pipeline is purged 3 to 4 times to completely remove the residual air in the high-pressure reactor 12. The preset generated pressure is A. When the experimental gas is introduced and the pressure in the high-pressure reactor 12 reaches 70% of the preset value A, the gas is introduced and the gas is stopped. The valve at the gas inlet pipeline 3 is closed, the magnetic stirrer 13 is turned on, and the speed is adjusted to 500 r / min.

[0047] Furthermore, in step S2, the reaction is started: the temperature inside the constant temperature device 6 required for the experiment is set, and after the temperature inside the high-pressure reactor 12 reaches the target value and becomes constant, the formation of hydrates at the gas-liquid interface is observed through the observation window 14 of the high-pressure reactor 12.

[0048] Furthermore, in step S2, pressurization is performed by pushing the hand pump 9 to slowly increase the pressure inside the high-pressure reactor 12. During this process, the pressure values ​​corresponding to different scales are recorded. Pressurization is performed approximately every 2 minutes, and each pressurization value is approximately 5% of the estimated value A (i.e., 5%A). If hydrate does not form, the pressure inside the high-pressure reactor 12 is continuously increased by pushing the hand pump 9 forward.

[0049] Further, in step S2, hydrate formation: If hydrate forms, the pressure reading will decrease significantly. Note that when the pressure starts to drop significantly or the temperature rises significantly, the pump pushing should be stopped immediately. When a large amount of hydrates are observed to form, immediately reduce the pressure inside the high-pressure reactor 12 using the hand pump 9 until there is a trace amount of hydrates remaining at the interface and maintain the pressure constant. Let the pressure when a small amount of hydrate formation can be observed be C. At this time, if A ≤ C, adjust the hand pump 9 to make the pressure reach the predicted value A; if C < A, then adjust the hand pump 9 to make the pressure drop to 96% of C (if the pressure of 96%C has been proven unable to form hydrates before, adjust to a relatively larger value), and let the pressure value at this time be D.

[0050] Wait for 1 hour. After 1 hour, if the pressure is stable and remains stable for more than 20 minutes, let the pressure at this time be E. At this time, if E = D, then E is the hydrate formation pressure; if the pressure is still changing after 1 hour, wait until the pressure stops changing and remains stable for more than 20 minutes, and then let the stable pressure at this time be E. If E > D and the hydrates have completely disappeared, and E is equivalent to the calibrated pressure corresponding to the pump pushing when no hydrates are formed, it means that the hydrates have completely decomposed. D and E are less than the hydrate formation pressure. Redefine A = min{E + 0.06 MPa, 1.05E}, and restart the experiment from the beginning of hydrate formation; if E > D, but the hydrates still exist, continue to observe; if D > E and D - E > min{0.05E, 0.05 MPa}, redefine A = E, and restart the experiment from the start of the reaction after the hydrates have completely decomposed. When 0 < D - E < min{0.05E, 0.05 MPa}, continue to observe.

[0051] To verify the effect of the composite promoter (TBAB > 0), the following control groups and experimental groups were set up:

[0052] Comparative example 1: Without any promoter, as the baseline;

[0053] Comparative example 2: Single kinetic promoter (OGP);

[0054] Comparative example 3: Single thermodynamic promoter (TBAB);

[0055] Comparative example 4: Single thermodynamic promoter (TMAC);

[0056] Comparative example 5: Binary composite promoter (TBAB + OGP);

[0057] Comparative example 6: Binary composite promoter (TMAC + OGP);

[0058] Comparative Example 7: Four formulations of the ternary composite accelerator (TBAB + TMAC + OGP) from the reference examples are used to demonstrate the optimization effect under different formulations. The experiment was repeated three times and the average value was taken. The results are shown in the table below:

[0059] Experimental conditions Accelerator concentration (wt%) Generation pressure (MPa) Induction time (minutes) Hydrate stability (hours) Relative pressure reduction rate Relative shortening rate of induction time Comparative Example 1: No accelerator - 4.5 60 24 - - Comparative Example 2: Single OGP OGP: 0.1 4.0 30 36 11.1% 50.0% Comparative Example 3: Single TBAB TBAB: 30 3.5 40 40 22.2% 33.3% Comparative Example 4: Single TMAC TMAC: 15 3.2 50 45 28.9% 16.7% Comparative Example 5: TBAB+OGP TBAB: 25, OGP: 0.5 2.8 22 55 37.8% 63.3% Comparative Example 6: TMAC+OGP TMAC: 10, OGP: 0.4 2.9 20 70 35.6% 66.7% Ternary composite 1 TBAB: 20, TMAC: 5, OGP: 0.3 2.3 15 75 48.9% 75.0% Ternary composite 2 TBAB:15, TMAC:8, OGP:0.8 2.5 10 80 44.4% 83.3% Ternary composite 3 TBAB:25, TMAC:15, OGP:0.1 2.0 20 85 55.6% 66.7% Ternary composite 4 TBAB:18, TMAC:10, OGP:0.4 2.4 16 >90 46.7% 73.3%

[0060] The above demonstrates the application effects of the composite accelerators TBAB, TMAC, and OGP at different ratios. The experimental conditions were set at 5℃ and a stirring speed of 500 r / min. The experimental data show that the composite accelerators can significantly reduce the CO2 hydrate formation pressure and shorten the induction time.

[0061] Furthermore, in step S2, the hydrate formation pressure is determined. After waiting for three hours, if the hydrate completely disappears and the final pressure reading is equivalent to the scale pressure corresponding to the pump push when no hydrate has formed, it indicates that the hydrate has been completely dissolved. The pressure reading at this time is defined as F, and A = min{F + 0.03 MPa, 1.025 F} is redefined. The experiment is repeated from the start of the reaction. If a small amount of hydrate still exists at this time, then the pressure F is the hydrate formation pressure under this condition, and the industrial-scale sealing of hydrate can be attempted at this pressure.

[0062] The constant temperature device 6 in this application is a constant temperature air bath with a temperature range of 253.15 K to 323.15 K. A temperature sensor 15 (Pt100) is installed inside the high-pressure reactor 12 to measure the internal temperature of the reactor 12, with a measurement accuracy of ±0.1 K. The pressure value is measured in real time by the first pressure sensor 8 and the second pressure sensor 16, with a measurement range of 0 to 20 MPa and a measurement accuracy of ±0.01 MPa. In this experiment, the solution was prepared using an analytical balance CPA225D (weighing accuracy of 0.01 g). This application combines TBAB, TMAC, and OGP in the aforementioned ratio to form a composite promoter. TBAB can significantly reduce the pressure required for CO2 to form hydrates. TBAB can participate in hydrate formation because it can occupy the hollow pores in the hydrate structure during the hydrate formation process, increasing the pore filling rate and promoting hydrate stability. OGP can increase the reaction rate of the hydration reaction. By introducing TMAC, its smaller molecular size may complement TBAB, potentially leading to a denser and more complete hydrate crystal structure. TMAC possesses smaller molecular weight and higher solubility in water, exhibiting a unique thermodynamic promoting effect under varying temperature and pressure conditions. The addition of TMAC can alter the phase equilibrium conditions of the hydrate, allowing it to form under milder conditions, which is significant for reducing energy consumption and operational complexity in the storage process. By comparing the stability maintenance time of the hydrate under experimental conditions, the potential of the composite promoter in improving the short- to medium-term stability of hydrates is verified. This clarifies that this application can promote the formation of CO2 hydrates, solving the problems of high production pressure and slow reaction rate in the hydration reaction, making the hydrate method for CO2 storage more industrially viable.

[0063] The above technical features constitute the embodiments of this application, which have strong adaptability and implementation effect. Non-essential technical features can be added or removed according to actual needs to meet the needs of different situations.

Claims

1. A complex promoter for sequestration of carbon dioxide as hydrate, characterized by: The complexing agent includes thermodynamic promoter tetrabutyl ammonium bromide (TBAB), tetramethyl ammonium chloride (TMAC) and surfactant octyl glucoside (OGP), and the mass percentage concentration of the three after mixing with water is TBAB: 20wt%, TMAC: 5wt%, OGP: 0.3wt%.

2. Use of a complex promoter of carbon dioxide hydrate sequestration according to claim 1, characterized in that: The method comprises the following steps, S1. Injecting the complexing agent and the experimental solution into the high-pressure reactor from the inlet and outlet pipeline, then closing the control valve at the gas cylinder, the control valve at the inlet and outlet pipeline, the control valve at the exhaust pipeline, and then starting the vacuum pump to remove the gas in the high-pressure reactor and the pipelines, and the vacuumizing time is 30 minutes; S2. Controlling the temperature of the thermostat to keep the temperature in the high-pressure reactor stable, then opening the control valve at the gas cylinder, closing the control valve at the vacuum pump, and introducing CO2 gas into the high-pressure reactor, and pressurizing the high-pressure reactor with the hand pump, and stopping the gas introduction when the set pressure is reached, and starting the magnetic stirrer below the high-pressure reactor when the temperature in the high-pressure reactor drops to the set temperature, and starting the timing, and when the CO2 hydrate is generated, the time required is the induction time of the CO2 hydrate; Hydrate generation: if hydrate is generated, the pressure indicator will decrease obviously, and the pump should be stopped immediately when the pressure starts to decrease obviously or the temperature increases obviously; If a large amount of hydrate is observed to be generated, the pressure in the high-pressure reactor should be immediately reduced by the hand pump until a trace amount of hydrate remains at the interface and the pressure remains unchanged; If a small amount of hydrate is observed to be generated, the pressure at this time is C, and if A≤C, the pressure is adjusted to the estimated value A by the hand pump; If C<A, the pressure is adjusted to 96% of C by the hand pump, and the pressure at this time is D; After waiting for 1 hour, if the pressure is stable and stable for more than 20 minutes after 1 hour, the pressure at this time is E, and if E=D, E is the hydrate generation pressure; If the pressure still changes after 1 hour, wait until the pressure no longer changes and can be stable for more than 20 minutes, and then the stable pressure at this time is E, and if E>D and the hydrate completely disappears, and E is equivalent to the scale pressure when the pump is not generated, it is indicated that the hydrate is completely dissolved, D and E are less than the hydrate generation pressure, A is redefined as min{E+0.06 MPa, 1.05E}, and the experiment is retested; If E>D, but the hydrate still exists, continue to observe; If D>E and D-E>min{0.05E, 0.05 MPa}, A is redefined as E, and the experiment is restarted after the hydrate is completely dissolved When 0<D-E<min{0.05E, 0.05 MPa}, continue to observe; After waiting for 3 hours, if the hydrate completely disappears, and the final pressure indicator is equivalent to the scale pressure when the pump is not generated, it is indicated that the hydrate is completely dissolved, the pressure indicator at this time is defined as F, and A is redefined as min{F+0.03 MPa, 1.025F}, and the experiment is retested; ​ ​ If there is still a small amount of hydrate at this time, the pressure F is the hydrate formation pressure under this condition; S3. When the temperature and pressure in the high-pressure reactor remain unchanged, it is considered that the CO2 hydrate is completely formed, the control valve on the exhaust line is opened, the exhaust speed is controlled, the temperature in the high-pressure reactor is kept constant, the temperature and pressure data are transmitted to the data recording and display device through the temperature sensor and the first and second pressure sensors, the temperature and pressure values of the CO2 hydrate in the decomposition process are recorded, and the balance point of the CO2 storage by the hydrate method is found by observing the observation window; S4. After the exhaust valve is opened, the hydrate begins to decompose, and when obvious bright spots appear in the observation window, the phase equilibrium data at this time, i.e. the balance point of the CO2 storage by the hydrate method, is recorded.

3. Use of a hydrate sequestering composite accelerator of carbon dioxide according to claim 2, characterized in that: In step S2, pressurization: push the hand pump to slowly increase the pressure in the high-pressure reactor, record the corresponding pressure values at different scales in the process, add pressure every 2 min, and each pressure increase value is 5% of the estimated value A. If the hydrate continues to be generated, the pressure in the high-pressure reactor is continuously increased by pushing the hand pump.

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