Sodium acetate hydrate inhibitor for carbon dioxide pipeline flow assurance

Abstract

The application relates to a sodium acetate hydrate inhibitor containing sodium acetate for carbon dioxide conveying pipeline flow guarantee, which comprises sodium acetate, methanol, poly (N-vinyl caprolactam), polyoxyethylene sorbitol monooleate, and the mass percentage concentration of the four after being mixed with a sodium chloride solution as a solvent is as follows: sodium acetate 50-60 wt%, methanol 25-30 wt%, poly (N-vinyl caprolactam) 0.01-1 wt%, and polyoxyethylene sorbitol monooleate 0.01-0.1 wt%. In the application, the composite use of sodium acetate, methanol, poly (N-vinyl caprolactam) and polyoxyethylene sorbitol monooleate enhances the effect of a single inhibitor, the use range is more extensive, a better inhibiting effect is achieved while the methanol use concentration is reduced, carbon dioxide hydrate generation can be better inhibited, the inhibitor cost is reduced by mixed use, the amount of the mixture is reduced, and the toxicity and pollution of the inhibitor are weakened.

Description

TECHNICAL FIELD

[0001] The present application relates to a hydrate inhibitor, in particular to a sodium acetate hydrate inhibitor for carbon dioxide pipeline flow assurance. BACKGROUND

[0002] In the process of carbon dioxide capture, transportation and storage (CCUS), long-distance pipeline transportation is one of the key technical links. However, during the transportation process, carbon dioxide and water in the pipeline can easily form hydrates under certain temperature and pressure, which can block the pipeline and cause a decrease in transportation efficiency or even interruption, posing a threat to production safety. Traditional hydrate inhibitors have problems such as high cost, unstable effect or poor environmental protection, which are difficult to meet the actual demand. Studies have shown that organic inhibitors have hydrophilic groups that can form hydrogen bonds with water molecules, while electrolytes bind water in the solvation shell of dissolved ions. This will reduce the force that inhibits the formation of hydrates.

[0003] Problems existing in the prior art:

[0004] 1. Cost: Thermodynamic inhibitors such as alcohols (methanol, ethylene glycol) and electrolytes (such as CaCl2). When methanol is used as an inhibitor, its part in the gas phase is usually not recovered, and the liquid phase aqueous solution can be recycled after distillation, but the economic efficiency of recycling needs to be analyzed according to the specific situation such as the amount of treated gas. Kinetic inhibitors have a lower concentration, but their inhibitory effect is limited, and they may need to increase the dosage or use more efficient inhibitors to achieve the desired effect, thereby increasing the cost.

[0005] 2. Environmental problems: Methanol inhibitors have moderate toxicity, although their use has been limited to some extent, but the disposal of waste liquid is still a problem, and measures such as reinjection or incineration may have some impact on the environment;

[0006] 3. Technical limitations: Kinetic inhibitors provide a new inhibition approach, but their molecular structure is not ideal, the inhibitory activity is low, and they can only prevent the formation of gas hydrates when oil and water coexist, and the effect is selective with oil and gas systems, which limits their application range and effect.

[0007] The commonly used hydrate inhibitors have large dosage, high cost and serious environmental pollution, so the research and development of environmentally friendly hydrate inhibitors have attracted widespread attention. SUMMARY

[0008] The purpose of the present application is to provide a sodium acetate hydrate inhibitor for carbon dioxide pipeline flow assurance with small dosage, low cost and green pollution.

[0009] The application is implemented by using sodium acetate hydrate inhibitor containing sodium acetate, methanol, poly (N-vinyl caprolactam), polyoxyethylene sorbitol monooleate, and sodium chloride solution as solvent, wherein the mass percentage concentration of sodium acetate, methanol, poly (N-vinyl caprolactam), and polyoxyethylene sorbitol monooleate is 50-60 wt% of sodium acetate, 25-30 wt% of methanol, 0.01-1 wt% of poly (N-vinyl caprolactam), and 0.01-0.1 wt% of polyoxyethylene sorbitol monooleate.

[0010] Further, the mass percentage concentration of sodium acetate, methanol, poly (N-vinyl caprolactam), and polyoxyethylene sorbitol monooleate is 50 wt% of sodium acetate, 25 wt% of methanol, 0.01 wt% of poly (N-vinyl caprolactam), and 0.01 wt% of polyoxyethylene sorbitol monooleate.

[0011] Further, the mass percentage concentration of sodium acetate, methanol, poly (N-vinyl caprolactam), and polyoxyethylene sorbitol monooleate is 50 wt% of sodium acetate, 25 wt% of methanol, 0.01 wt% of poly (N-vinyl caprolactam), and 0.1 wt% of polyoxyethylene sorbitol monooleate.

[0012] Further, the mass percentage concentration of sodium acetate, methanol, poly (N-vinyl caprolactam), and polyoxyethylene sorbitol monooleate is 60 wt% of sodium acetate, 25 wt% of methanol, 1 wt% of poly (N-vinyl caprolactam), and 0.1 wt% of polyoxyethylene sorbitol monooleate.

[0013] Further, the mass percentage concentration of sodium acetate, methanol, poly (N-vinyl caprolactam), and polyoxyethylene sorbitol monooleate is 60 wt% of sodium acetate, 30 wt% of methanol, 1 wt% of poly (N-vinyl caprolactam), and 0.1 wt% of polyoxyethylene sorbitol monooleate.

[0014] Further, the mass percentage concentration of sodium acetate, methanol, poly (N-vinyl caprolactam), and polyoxyethylene sorbitol monooleate is 50 wt% of sodium acetate, 25 wt% of methanol, 1 wt% of poly (N-vinyl caprolactam), and 0.1 wt% of polyoxyethylene sorbitol monooleate.

[0015] Further, the sodium chloride solution is composed of 3.5% NaCl and 96.5% deionized water.

[0016] Due to the implementation of the above technical solutions, the sodium acetate in the present application can provide stable inhibition effect under different operating conditions. Methanol can further enhance the inhibition effect of the inhibitor, but considering the cost and environmental factors, it needs to be controlled within a reasonable range. Poly (N-vinyl caprolactam) (PVCap) as a kinetic inhibitor (KHI). Polyoxyethylene sorbitan monooleate (Tween-80) as a non-ionic anti-agglomeration / dispersant, wetting / coating the surface of the hydrate particles, preventing agglomeration and adhesion.

[0017] The hydrate inhibitor containing sodium acetate organic carboxylate salt combines the characteristics of organic inhibitors and electrolytes. The strength of thermodynamic inhibition is related to the chain length of organic carboxylate, and long-chain organic carboxylate has a more obvious effect on aw (water activity), so it has a stronger thermodynamic inhibition effect on hydrate. By comparing the thermodynamic inhibition effect of sodium acetate, NaCl and KCl on CO2 hydrate. The results show that the ΔP (VLH phase equilibrium pressure change) of the sodium acetate solution system is higher than that of the NaCl and KCl solution systems. The thermodynamic inhibition effect of sodium acetate is stronger than that of NaCl and KCl. This is because the effect of acetate ion on aw is stronger than that of chloride ion. DETAILED DESCRIPTION

[0018] The technical solutions in the embodiments of the present application will be described below in a clear and complete manner. Obviously, the described embodiments are only a part of the embodiments of the present application, not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative labor are within the scope of protection of the present application.

[0019] Embodiment: A hydrate inhibitor containing sodium acetate for carbon dioxide transportation pipeline flow assurance, comprising sodium acetate, methanol, poly (N-vinyl caprolactam), and polyoxyethylene sorbitan monooleate, which are mixed with sodium chloride solution as a solvent, and the mass percentage concentration of the four is sodium acetate 50-60 wt%, methanol 25-30 wt%, poly (N-vinyl caprolactam) 0.01-1 wt%, and polyoxyethylene sorbitan monooleate 0.01-0.1 wt%.

[0020] Further, the mass percentage concentration of sodium acetate, methanol, poly (N-vinyl caprolactam), and polyoxyethylene sorbitan monooleate is sodium acetate 50 wt%, methanol 25 wt%, poly (N-vinyl caprolactam) 0.01 wt%, and polyoxyethylene sorbitan monooleate 0.01 wt%, respectively.

[0021] Further, the mass percentage concentration of sodium acetate, methanol, poly(N-vinyl caprolactam), and polyoxyethylene sorbitan monooleate is 50wt% sodium acetate, 25wt% methanol, 0.01wt% poly(N-vinyl caprolactam), and 0.1wt% polyoxyethylene sorbitan monooleate, respectively.

[0022] Further, the mass percentage concentration of sodium acetate, methanol, poly(N-vinyl caprolactam), and polyoxyethylene sorbitan monooleate is 60wt% sodium acetate, 25wt% methanol, 1wt% poly(N-vinyl caprolactam), and 0.1wt% polyoxyethylene sorbitan monooleate, respectively.

[0023] Further, the mass percentage concentration of sodium acetate, methanol, poly(N-vinyl caprolactam), and polyoxyethylene sorbitan monooleate is 60wt% sodium acetate, 30wt% methanol, 1wt% poly(N-vinyl caprolactam), and 0.1wt% polyoxyethylene sorbitan monooleate, respectively.

[0024] Further, the mass percentage concentration of sodium acetate, methanol, poly(N-vinyl caprolactam), and polyoxyethylene sorbitan monooleate is 50wt% sodium acetate, 25wt% methanol, 1wt% poly(N-vinyl caprolactam), and 0.1wt% polyoxyethylene sorbitan monooleate, respectively.

[0025] Further, the sodium chloride solution is a mixture of 3.5% NaCl and 96.5% deionized water, which is used to simulate seawater.

[0026] The verification of the inhibition effect is carried out by the following experimental device, which is prior art, including a thermostatic device with a cavity, a high-pressure reaction kettle for hydration reaction is arranged in the thermostatic device, an observation window is arranged on the surface of the high-pressure reaction kettle, the cavity in the high-pressure reaction kettle is in communication with the lower part of a buffer tank arranged on the upper side of the high-pressure reaction kettle, a piston is arranged in the buffer tank, the cavity above the piston is connected with a hand pump through a pressurizing pipeline, the cavity below the piston is in communication with the cavity in the high-pressure reaction kettle, and the cavity below the piston is connected with a storage cylinder and a vacuum pump in parallel through an air inlet pipeline, the upper part of the cavity in the high-pressure reaction kettle is connected with an exhaust pipeline, and the lower part of the cavity in the high-pressure reaction kettle is connected with an inlet and outlet liquid pipeline.

[0027] Further, a magnetic stirrer is arranged at the bottom of the high-pressure reaction kettle, and a stirring end of the magnetic stirrer extends into the cavity in the high-pressure reaction kettle. The magnetic stirrer is used for uniform mixing of gas and liquid phases and strengthening of mass transfer in the kettle, and the speed thereof can be adjusted. The magnetic stirrer is prior art and is not the point of the present application, and the specific structure is not described in detail.

[0028] Further, the constant temperature device is a prior art, and the specific structure is not described in detail, which is not the application point of the present application. The second pressure sensor and the temperature sensor are connected with the data recording and display device circuit arranged outside the constant temperature device.

[0029] Further, the first pressure sensor is arranged at the pressurizing cavity of the hand pump, and the first pressure sensor is connected with the data recording and display device circuit arranged outside the constant temperature device.

[0030] The data recording and display device is used to record the pressure and temperature data returned by the first pressure sensor, the second pressure sensor and the temperature sensor, and is also a prior art, and the specific structure is not described in detail, which is not the application point of the present application.

[0031] Further, the control valves are arranged at the air inlet pipeline, the air outlet pipeline, the liquid inlet and outlet pipeline, and the communication parts of the air inlet pipeline and the gas storage bottle and the vacuum pump.

[0032] The related experiment includes the following steps:

[0033] S1. The experimental solution containing the sodium acetate hydrate inhibitor is injected into the high-pressure reaction kettle from the liquid inlet and outlet pipeline, and then the control valves at the gas storage bottle, the liquid inlet and outlet pipeline and the air outlet pipeline are closed, and the vacuum pump is started to remove the gas in the high-pressure reaction kettle and the pipelines, and the vacuum time is 30 minutes.

[0034] S2. The temperature of the constant temperature device is controlled to keep the temperature in the high-pressure reaction kettle stable, and then the control valve at the gas storage bottle is opened, the control valve at the vacuum pump is closed, CO2 gas is introduced into the high-pressure reaction kettle, the hand pump is used to pressurize the high-pressure reaction kettle, and the gas supply is stopped when the set pressure is reached. When the temperature in the high-pressure reaction kettle drops to the set temperature, the magnetic stirrer below the high-pressure reaction kettle is started, and the time is counted. With the generation of CO2 hydrate, when the CO2 hydrate crystal nucleus is observed in the observation window, the required time is the induction time of CO2 hydrate.

[0035] S3. When the temperature and pressure in the high-pressure reaction kettle remain unchanged, it is considered that the CO2 hydrate is completely generated, the control valve on the air outlet pipeline is opened, the exhaust speed is controlled (5-7 seconds for a pressure drop of 0.01 Mpa), the temperature in the high-pressure reaction kettle is kept constant, the temperature and pressure data are transmitted to the data recording and display device through the temperature sensor and the first pressure sensor and the second pressure sensor, 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.

[0036] 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, that is, the equilibrium point of the hydrate method for storing CO2.

[0037] Further, the experimental solution refers to a mixture of one or more of deionized water, NaCl, calcium chloride, sodium sulfate, etc.

[0038] Further, in step S2, the temperature in the high-pressure reactor is 2-10°C, the specific pressure is 3-5 Mpa, and the magnetic stirrer operates at a speed of 500 rpm.

[0039] Further, in step S1, the reactor is cleaned: open the control valves of the vacuum pump and the gas inlet pipeline, close the control valves of the liquid inlet and outlet pipeline and the exhaust pipeline, start the vacuum pump to vacuum the high-pressure reactor, then close the control valves of the vacuum pump and the gas inlet pipeline, open the control valves of the liquid inlet and outlet pipeline to suck in 80 ml of deionized water, start the magnetic stirrer to clean the high-pressure reactor 3-4 times, and the cleaned deionized water is discharged from the liquid inlet and outlet pipeline; then open the control valves of the vacuum pump and the gas inlet pipeline again, close the control valves of the liquid inlet and outlet pipeline, use the vacuum pump to vacuum the high-pressure reactor, close the control valves of the vacuum pump and the gas inlet pipeline, open the control valves of the liquid inlet and outlet pipeline to suck in the sodium acetate hydrate inhibitor containing the sodium acetate hydrate inhibitor described in the application 1-2 times, and the sodium acetate hydrate inhibitor containing the sodium acetate hydrate inhibitor is discharged from the liquid inlet and outlet pipeline; finally, inject 50 ml of the sodium acetate hydrate inhibitor containing the sodium acetate hydrate inhibitor described in the application and the experimental solution into the high-pressure reactor in a volume ratio of 1:25.

[0040] Further, in step S2, the gas is introduced: the experimental gas (CO2) is introduced from the gas cylinder into the high-pressure reactor, the pipelines are purged 3-4 times, the residual air in the high-pressure reactor is completely discharged, the expected generation pressure is set to A, the experimental gas is introduced and the pressure in the high-pressure reactor reaches 70% of the estimated value A, the valve at the gas inlet pipeline is closed, the magnetic stirrer is opened, and the speed is adjusted to 500 r / min.

[0041] Further, in step S2, the reaction is started: the temperature in the constant temperature device required for the experiment is set, and after the temperature in the high-pressure reactor reaches the target value and remains constant, the hydrate generation at the gas-liquid interface of the high-pressure reactor is observed through the observation window.

[0042] Further, in step S2, pressurization: push the hand pump to slowly increase the pressure in the high-pressure reactor, and record the pressure value corresponding to different scales during the process. Increase the pressure about every 2 minutes, and each time the pressure value is about 5% of the estimated value A (i.e. 5% A). If the hydrate does not generate continuously, increase the pressure in the high-pressure reactor by pushing the hand pump.

[0043] Further, in step S2, hydrate generation: if the hydrate generates, the pressure indicator will obviously decrease. Note that when the pressure begins to obviously decrease or the temperature obviously increases, immediately stop pushing the pump. If a large amount of hydrate is observed to generate, immediately reduce the pressure in the high-pressure reactor by pushing the hand pump until a trace amount of hydrate remains at the interface and the pressure is maintained. The pressure at which a small amount of hydrate is observed to appear is C, at this time, if A≤C, adjust the hand pump so that the pressure reaches the predicted value A; if C

[0044] Wait for 1 hour, and if the pressure is stable after 1 hour and stable for more than 20 minutes, the pressure at this time is E, at this time, if E=D, E is the hydrate generation pressure; if the pressure is still changing after 1 hour, wait until the pressure no longer changes and is stable for more than 20 minutes, and then the stable pressure at this time is E, if E>D and the hydrate completely disappears, and E is equivalent to the scale pressure corresponding to pushing the pump when the hydrate does not generate, it means that the hydrate completely dissolves, D and E are less than the hydrate generation pressure, redefine A=min{E+0.06 MPa, 1.05E}, and start the experiment again from the hydrate generation; if E>D, but the hydrate still exists, continue to observe; if D>E and D-E>min{0.05E, 0.05 MPa}, redefine A=E, and start the experiment again from the start of the reaction after the hydrate completely dissolves, and when 0<D-E<min{0.05E, 0.05 MPa}, continue to observe.

[0045] By verifying the ratio of the present application at different concentrations and comparing the phase equilibrium temperature and pressure under the action of sodium acetate alone at different concentrations, it is not difficult to find that the present application can effectively increase the phase equilibrium pressure, thereby avoiding the occurrence of pipeline blockage. The specific results are shown in the following table:

[0046]

[0047] The above experimental data show that the best ratio is 50wt% sodium acetate, 25wt% methanol, 1wt% poly(N-vinylcaprolactam), and 0.1wt% polyoxyethylene sorbitan monooleate. The hydrate inhibitor of the present application can significantly increase the phase equilibrium pressure of CO2 hydrate and effectively prevent hydrate plugging.

[0048] Sodium acetate, as an organic substance, has stability and chemical properties that help inhibit the formation of hydrates under certain conditions. Methanol, on the other hand, has low freezing point, high solubility, renewable, low corrosive, and other advantages in the field of thermodynamic inhibitors. The combination of the two can exert their respective advantages and provide more comprehensive and stable inhibition effect. By using sodium acetate and methanol together, more efficient inhibition effect can be achieved under different conditions. Sodium acetate may be more suitable for certain specific temperature or pressure conditions, while methanol may perform better under other conditions. The combination of the two can provide stable inhibition performance in a wider operating range. Methanol, as a renewable resource, its use helps to reduce the impact on the environment. Although the environmental impact of sodium acetate is relatively small, the use of the two together can reduce the potential environmental impact of a single inhibitor to some extent. The price of methanol is relatively low, and its use with sodium acetate can improve the inhibition effect, thereby reducing the amount of inhibitor used and further reducing costs. Both sodium acetate and methanol are common chemicals, easy to purchase and store. The operation of mixed use is relatively simple, which can be directly mixed or added to the natural gas system in a certain proportion.

[0049] Poly(N-vinylcaprolactam) (PVCap) and polyoxyethylene sorbitan monooleate (Tween-80) have complementary functions, where PVCap is a highly efficient kinetic inhibitor (KHI) that adsorbs to the surface of hydrate crystal nuclei through a polar lactam ring, forming a spatial barrier layer that significantly slows down the nucleation induction time and crystal growth rate, thereby inhibiting the formation and expansion of hydrate structures. Tween-80, as a non-ionic surfactant, mainly functions as an anti-agglomerant (AA) that coats the surface of generated hydrate particles with a hydrophilic-lipophilic amphiphilic structure, changing the particle wettability, enhancing its hydrophilicity, and effectively preventing particle aggregation and adhesion through steric hindrance, allowing the particles to exist in a finely dispersed state in the fluid, avoiding plugging. Tween-80 can form a mixed adsorption layer with PVCap at the interface, and the presence of Tween-80 helps PVCap molecules to enrich and orient at the gas-liquid interface, thereby improving the inhibition efficiency of PVCap. The combination of the two can build a "inhibition-dispersion" dual mechanism: PVCap delays bulk formation, and Tween-80 controls particle behavior, achieving synergistic effect at low addition amount. This composite system has both economy and operational feasibility, providing important technical support for deepwater oil and gas flow safety.

[0050] The above technical features constitute embodiments of the present application, which have strong adaptability and implementation effects. Unnecessary technical features can be added or removed according to actual needs to meet the needs of different situations.

Claims

1. Sodium acetate hydrate inhibitor for carbon dioxide pipeline flow assurance, comprising sodium acetate, methanol, poly (N-vinyl caprolactam), polyoxyethylene sorbitan monooleate, and sodium chloride solution as solvent, wherein the mass percentage concentration of sodium acetate is 50-60 wt%, the mass percentage concentration of methanol is 25-30 wt%, the mass percentage concentration of poly (N-vinyl caprolactam) is 0.01-1 wt%, and the mass percentage concentration of polyoxyethylene sorbitan monooleate is 0.01-0.1 wt%. The sodium chloride solution is a mixture of 3.5 wt% NaCl and 96.5 wt% deionized water.

2. The sodium acetate hydrate inhibitor for carbon dioxide pipeline flow assurance of claim 1, wherein: The mass percentage concentration of sodium acetate is 50 wt%, the mass percentage concentration of methanol is 25 wt%, the mass percentage concentration of poly (N-vinyl caprolactam) is 0.01 wt%, and the mass percentage concentration of polyoxyethylene sorbitan monooleate is 0.01 wt%.

3. The sodium acetate hydrate inhibitor for carbon dioxide pipeline flow assurance of claim 1, wherein: The mass percentage concentration of sodium acetate is 50 wt%, the mass percentage concentration of methanol is 25 wt%, the mass percentage concentration of poly (N-vinyl caprolactam) is 0.01 wt%, and the mass percentage concentration of polyoxyethylene sorbitan monooleate is 0.1 wt%.

4. The sodium acetate hydrate inhibitor for carbon dioxide pipeline flow assurance of claim 1, wherein: The mass percentage concentration of sodium acetate is 60 wt%, the mass percentage concentration of methanol is 25 wt%, the mass percentage concentration of poly (N-vinyl caprolactam) is 1 wt%, and the mass percentage concentration of polyoxyethylene sorbitan monooleate is 0.1 wt%.

5. The sodium acetate hydrate inhibitor for carbon dioxide pipeline flow assurance of claim 1, wherein: The mass percentage concentration of sodium acetate is 60 wt%, the mass percentage concentration of methanol is 30 wt%, the mass percentage concentration of poly (N-vinyl caprolactam) is 1 wt%, and the mass percentage concentration of polyoxyethylene sorbitan monooleate is 0.1 wt%.

6. The sodium acetate hydrate inhibitor for carbon dioxide pipeline flow assurance of claim 1, wherein: The mass percentage concentration of sodium acetate is 50 wt%, the mass percentage concentration of methanol is 25 wt%, the mass percentage concentration of poly (N-vinyl caprolactam) is 1 wt%, and the mass percentage concentration of polyoxyethylene sorbitan monooleate is 0.1 wt%.

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