Sodium propionate hydrate inhibitor for carbon dioxide pipeline flow assurance

Abstract

The application relates to a sodium propionate hydrate inhibitor containing sodium propionate for carbon dioxide conveying pipeline flow guarantee, which comprises sodium propionate, glycine, polyvinyl pyrrolidone and methanol, and the molar percentage of the four after being mixed with a sodium chloride solution as a solvent is as follows: 1-15mol% of sodium propionate, 1-15mol% of glycine, 0.1-1mol% of polyvinyl pyrrolidone and 5-60mol% of methanol. In the application, the composite use of sodium propionate, glycine, polyvinyl pyrrolidone and methanol enhances the effect of a single inhibitor, the use range is more extensive, better inhibiting effect can be achieved at a lower concentration, and the generation of carbon dioxide hydrate can be better inhibited. The mixed use reduces the cost of the inhibitor, reduces the use amount of the mixture and weakens the toxicity and pollution of the inhibitor.

Description

Technical Field

[0001] This application relates to a hydrate inhibitor, and more particularly to a sodium propionate hydrate inhibitor for ensuring the flow of carbon dioxide transport pipelines. Background Technology

[0002] Hydrates are solid compounds formed by the combination of gas and water under specific temperature and pressure conditions. Pipeline transportation is usually carried out under low temperature and high pressure conditions, which is conducive to the formation of hydrates. Therefore, when a large amount of carbon dioxide hydrates are formed, it will block the pipeline, affect the normal transportation of gas, and even cause the pipeline to rupture, resulting in economic losses. The inhibition of hydrates is now mainly divided into two categories: physical methods and chemical methods. Physical methods mainly include dehydration, insulation, heating, decompression and coating. Chemical methods mainly include adding thermodynamic inhibitors (THIs), kinetic inhibitors (KHIs) and anti-agglomeration agents (AAs). At present, chemical inhibitors are widely used to prevent the formation of hydrates, among which methanol and ethylene glycol are the most widely used. These inhibitors are usually used in large quantities, have high costs and serious environmental problems (thermodynamic inhibitors related literature: Xu Weixiu, Li Qijing, Chen Guangjin. Research progress of natural gas hydrate inhibitors [J]. Chemical Industry and Engineering Progress, 2006, (11): 1289-1293+1300).

[0003] Currently, the main methods for preventing hydrate formation in pipelines include heating, decompression, dehydration, and chemical methods. Chemical methods typically use chemicals to inhibit hydrate formation or slow down hydrate polymerization, and these methods do not interfere with normal pipeline flow. Injecting thermodynamic inhibitors such as methanol and ethylene glycol is the most mature and commonly used method for preventing hydrate formation in pipelines. It prevents hydrate formation by shifting the hydrate stability region to high-pressure and low-temperature regions. However, thermodynamic inhibitors require large quantities, which can easily cause environmental pollution; the typical dosage is about 20-60 wt% (Reference: Lim WV, Metaxas JP, Stanwix LP, et al. Gas hydrate formation probability and growth rate as a function of kinetic hydrate inhibitor (KHI) concentration[J]. Chemical Engineering Journal, 2020, 388: 124177-124177).

[0004] Currently used hydrate inhibitors are characterized by large dosages, high costs, and serious environmental pollution. Therefore, the research and development of environmentally friendly hydrate inhibitors has attracted widespread attention. Summary of the Invention

[0005] The application aims to provide a sodium propionate hydrate inhibitor with small dosage, low cost, green and no pollution for flow protection of carbon dioxide conveying pipeline.

[0006] The application is implemented as follows: the sodium propionate hydrate inhibitor for flow protection of carbon dioxide conveying pipeline comprises sodium propionate, glycine, polyvinyl pyrrolidone and methanol, and the molar percentage of the four after being mixed with sodium chloride solution as a solvent is as follows: 1-15mol% of sodium propionate, 1-15mol% of glycine, 0.1-1mol% of polyvinyl pyrrolidone and 5-60mol% of methanol.

[0007] Further, the molar percentage of sodium propionate, glycine, polyvinyl pyrrolidone and methanol is as follows: 1mol% of sodium propionate, 1mol% of glycine, 0.1mol% of polyvinyl pyrrolidone and 60mol% of methanol.

[0008] Further, the molar percentage of sodium propionate, glycine, polyvinyl pyrrolidone and methanol is as follows: 1mol% of sodium propionate, 15mol% of glycine, 0.1mol% of polyvinyl pyrrolidone and 50mol% of methanol.

[0009] Further, the molar percentage of sodium propionate, glycine, polyvinyl pyrrolidone and methanol is as follows: 15mol% of sodium propionate, 1mol% of glycine, 0.1mol% of polyvinyl pyrrolidone and 50mol% of methanol.

[0010] Further, the molar percentage of sodium propionate, glycine, polyvinyl pyrrolidone and methanol is as follows: 1mol% of sodium propionate, 1mol% of glycine, 1mol% of polyvinyl pyrrolidone and 50mol% of methanol.

[0011] Further, the molar percentage of sodium propionate, glycine, polyvinyl pyrrolidone and methanol is as follows: 5mol% of sodium propionate, 8mol% of glycine, 0.5mol% of polyvinyl pyrrolidone and 5mol% of methanol.

[0012] Further, the sodium chloride solution is composed of 3.5% NaCl and 96.5% deionized water.

[0013] Due to the implementation of the above technical solution, the compound use of sodium propionate, glycine, polyvinyl pyrrolidone and methanol in the application enhances the effect of single inhibitor, has a wider use range, achieves better inhibition effect at a lower concentration, and can better inhibit the generation of carbon dioxide hydrate. The mixed use reduces the cost of the inhibitor, reduces the dosage of the mixture, and weakens the toxicity and pollution of the inhibitor.

[0014] The hydrate inhibitor of glycine + sodium propionate + polyvinyl pyrrolidone + methanol hydrate has a significant increase in VLH equilibrium pressure change (ΔP). The sodium salt of organic carboxylic acid molecules does not participate in the formation of the hydrate crystal structure, but only exists in the liquid phase. When the hydrate crystal consumes water molecules to form, the concentration of the additive in the remaining liquid phase aqueous solution increases. This further inhibits the formation of hydrate crystals, and only sI type hydrates exist in the solution. The present application has obvious thermodynamic inhibition effect on carbon dioxide hydrate, which significantly reduces the formation of hydrate, avoids the blockage of hydrate in the pipeline transportation of carbon dioxide, reduces the maintenance cost, and avoids the potential hidden danger in production. DETAILED DESCRIPTION

[0015] 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, rather than 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 fall within the scope of protection of the present application.

[0016] Embodiment: A hydrate inhibitor containing sodium propionate for carbon dioxide pipeline flow protection, comprising sodium propionate, glycine, polyvinyl pyrrolidone, methanol, and sodium chloride solution as a solvent, the molar percentage of the four after mixing is sodium propionate 1-15 mol%, glycine 1-15 mol%, polyvinyl pyrrolidone 0.1-1 mol%, and methanol 5-60 mol%.

[0017] Further, the molar percentage of sodium propionate, glycine, polyvinyl pyrrolidone, and methanol is sodium propionate 1 mol%, glycine 1 mol%, polyvinyl pyrrolidone 0.1 mol%, and methanol 60 mol%.

[0018] Further, the molar percentage of sodium propionate, glycine, polyvinyl pyrrolidone, and methanol is sodium propionate 1 mol%, glycine 15 mol%, polyvinyl pyrrolidone 0.1 mol%, and methanol 50 mol%.

[0019] Further, the molar percentage of sodium propionate, glycine, polyvinyl pyrrolidone, and methanol is sodium propionate 15 mol%, glycine 1 mol%, polyvinyl pyrrolidone 0.1 mol%, and methanol 50 mol%.

[0020] Further, the molar percentage of sodium propionate, glycine, polyvinyl pyrrolidone, and methanol is sodium propionate 1 mol%, glycine 1 mol%, polyvinyl pyrrolidone 1 mol%, and methanol 50 mol%.

[0021] Further, the sodium chloride solution is a mixture of 3.5% NaCl and 96.5% deionized water by mass percentage, which is used to simulate seawater.

[0022] 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 communicated 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 communicated with the cavity in the high-pressure reaction kettle, the cavity below the piston is connected with a gas storage bottle and a vacuum pump in parallel through a gas inlet pipeline, the upper part of the cavity in the high-pressure reaction kettle is communicated with a gas outlet pipeline, and the lower part of the cavity in the high-pressure reaction kettle is communicated with a liquid inlet and outlet pipeline.

[0023] 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.

[0024] Further, the thermostatic device is prior art and is not the point of the present application, and the specific structure is not described in detail. A second pressure sensor and a temperature sensor are arranged in the thermostatic device, and the second pressure sensor and the temperature sensor are connected with a data recording and display device circuit arranged outside the thermostatic device.

[0025] Further, a 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 thermostatic device.

[0026] 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. The data recording and display device is also prior art and is not the point of the present application, and the specific structure is not described in detail.

[0027] Further, control valves are arranged at the gas inlet pipeline, the gas outlet pipeline, the liquid inlet and outlet pipeline, and the communication positions of the gas inlet pipeline with the gas storage bottle and the vacuum pump.

[0028] The related experiment includes the following steps:

[0029] S1. The sodium propionate hydrate inhibitor and the experimental solution are injected into the high-pressure reaction kettle from the liquid inlet and outlet pipeline, then the control valves at the gas storage bottle, the liquid inlet and outlet pipeline and the gas 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 min.

[0030] S2. Control the temperature of the thermostat to keep the temperature in the high-pressure reactor stable, then open the control valve at the gas cylinder, close the control valve at the vacuum pump, and introduce CO2 gas into the high-pressure reactor. Use the hand pump to pressurize the high-pressure reactor, stop the gas introduction when the set pressure is reached, and wait until the temperature in the high-pressure reactor drops to the set temperature. Turn on the magnetic stirrer below the high-pressure reactor and start timing. As CO2 hydrate forms, visible CO2 hydrate nuclei appear in the observation window. The time required is the induction time of CO2 hydrate.

[0031] S3. When the temperature and pressure in the high-pressure reactor remain unchanged, it is considered that CO2 hydrate has been completely formed. Open the control valve on the exhaust line to control the exhaust speed (5-7 seconds, pressure drop 0.01 Mpa). Keep the temperature in the high-pressure reactor 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. Record the temperature and pressure values of CO2 hydrate during the decomposition process, and find the equilibrium point of CO2 storage by hydrate method by observing the observation window.

[0032] S4. After opening the exhaust valve, the hydrate begins to decompose. When obvious bright spots appear in the observation window, record the phase equilibrium data at this time, which is the equilibrium point of CO2 storage by hydrate method.

[0033] Further, the experimental solution refers to a mixture of one or more of deionized water, NaCl, calcium chloride, sodium sulfate, etc.

[0034] Further, in step S2, the temperature in the high-pressure reactor is 2-10°C, and the specific pressure is 3-5 Mpa. When the magnetic stirrer is working, the speed is 500 rpm.

[0035] Further, in step S1, the reactor is cleaned: open the control valves at the vacuum pump and gas inlet line, close the control valves at the liquid inlet and outlet lines and the exhaust line, start the vacuum pump to vacuum the high-pressure reactor, then close the control valves at the vacuum pump and gas inlet line, open the control valve at the liquid inlet and outlet line to suck in 80 ml of deionized water, turn on the magnetic stirrer to clean the high-pressure reactor 3-4 times, and then the deionized water is discharged through the liquid inlet and outlet line. Then open the control valves at the vacuum pump and gas inlet line again, close the control valve at the liquid inlet and outlet line, and use the vacuum pump to vacuum the high-pressure reactor. Close the control valves at the vacuum pump and gas inlet line, open the control valve at the liquid inlet and outlet line to suck in the propionic acid sodium hydrate inhibitor of the application for 1-2 times, and then the propionic acid sodium hydrate inhibitor is discharged through the liquid inlet and outlet line. Finally, inject 50 ml of the propionic acid sodium hydrate inhibitor and experimental solution of the application into the high-pressure reactor in a volume ratio of 1:25.

[0036] Further, in step S2, the air inlet: the experimental gas (CO2) from the gas cylinder into the high-pressure reactor, the pipeline for 3 ~ 4 times of purging, the high-pressure reactor residual air completely discharged after the preset pressure generation pressure estimate value is A, the experimental gas and make the high-pressure reactor pressure to estimate the value of 70% stop air inlet, close the valve at the air inlet pipeline, open the magnetic stirrer, adjust the speed to 500 r / min.

[0037] Further, in step S2, open the reaction: set the temperature required for the experiment in the thermostat, wait for the high-pressure reactor temperature reaches the target value and constant, through the observation window of the high-pressure reactor gas-liquid interface hydrate formation.

[0038] Further, in step S2, pressurization: push the hand pump to make the high-pressure reactor pressure slowly rises, the process record the corresponding pressure value at different scales, about every 2 min plus pressure, each pressure value is about 5% of the estimated value A (ie 5% A). If the hydrate continues to generate, through the hand pump to increase the pressure in the high-pressure reactor.

[0039] Further, in step S2, hydrate formation: if the hydrate, the pressure will be significantly reduced. Note when the pressure began to drop significantly or significantly increased temperature should be stopped immediately push pump. If observed when there is a large amount of hydrate formation immediately through the hand pump to reduce the pressure in the high-pressure reactor, until the interface residual trace hydrate and maintain the pressure. Allow to observe the emergence of a small amount of hydrate pressure for C, at this time if A≤C, adjust the hand pump so that the pressure reaches the predicted value A; if C < A, then adjust the hand pump so that the pressure is reduced to 96% of C (if 96% C pressure has been proven to be unable to form hydrates, adjust to a relatively larger value), and the pressure value at this time is D.

[0040] Wait for 1 hour, if the pressure is stable and stable for more than 20 minutes after 1 hour, let the pressure at this time be E, if E=D at this time, then E is the hydrate formation pressure; if the pressure is still changing after 1 hour, wait until the pressure no longer changes and can be stable for more than 20 minutes, then let the stable pressure at this time be E, if E>D and the hydrate completely disappears, and E is equivalent to the scale pressure corresponding to the push pump when the hydrate is not generated, then it is indicated that the hydrate is completely dissolved, D and E are less than the hydrate formation pressure, redefine A=min{E+0.06 MPa, 1.05E}, and start the experiment again from the beginning of the hydrate formation; if E>D, but the hydrate still exists, continue to observe; if D>E and D-E>min{0.05E, 0.05 MPa}, then redefine A=E, wait for the hydrate to completely dissolve and start the experiment again from the beginning of the reaction, and when 0<D-E<min{0.05E, 0.05 MPa}, continue to observe.

[0041] To verify the effect of the hydrate inhibitor of the present application, the present patent simulates the actual seawater situation NaCl (3.5%) and deionized water (96.5%) by the concentration of sodium chloride in deionized water. The inhibitors are selected as sodium propionate (0-5 mol%) + methanol (0-60 mol%) + glycine (0-8 mol%) + polyvinyl pyrrolidone (0-0.5 mol%). The experimental temperature range is 273.65-281.65 K. The experimental (vapor-liquid aqueous solution-solid hydrate) equilibrium data of carbon dioxide hydrate in the sodium salt of organic carboxylic acid system in terms of temperature T, pressure P, and molar fraction x of the liquid phase salt:

[0042]

[0043] The present application selects the N-NRTL-NRF activity model of the electrolyte solution, and considers the contribution of the dissolved gas and the electrolyte when calculating the water activity. The thermodynamic model of the hydrate is selected as the Chen-Guo model, which is proposed by Chen and Guo on the basis of assuming the double-process hydrate initiation mechanism of CO2 hydrate formation. A quasi-chemical reaction process centered on the dissolved gas molecules, and water molecules are connected by hydrogen bonds to form basic hydrates. The above experimental data show that the best ratio is 8 mol% of glycine + 5 mol% of sodium propionate + 0.5 mol% of polyvinyl pyrrolidone + 5 mol% of methanol, and the hydrate inhibitor of the present application can significantly increase the CO2 hydrate formation pressure (i.e. GLHE pressure), and can effectively prevent hydrate plugging.

[0044] The above technical features constitute an embodiment of the present application, which has strong adaptability and implementation effect. Non-essential technical features can be added or subtracted according to actual needs to meet the needs of different situations.

Claims

1. Sodium propionate hydrate inhibitor for carbon dioxide pipeline flow assurance characterized by: Sodium propionate, glycine, polyvinyl pyrrolidone, methanol, after mixing with sodium chloride solution as solution, the molar percentage is, sodium propionate 1-15mol%, glycine 1-15mol%, polyvinyl pyrrolidone 0.1-1mol%, methanol 5-60mol%; The sodium chloride solution is composed of 3.5% NaCl and 96.5% deionized water.

2. The sodium propionate hydrate inhibitor for carbon dioxide pipeline flow assurance of claim 1, wherein: The molar percentage of sodium propionate, glycine, polyvinyl pyrrolidone, methanol is sodium propionate 1mol%, glycine 1mol%, polyvinyl pyrrolidone 0.1mol%, methanol 60mol%.

3. The sodium propionate hydrate inhibitor for carbon dioxide pipeline flow assurance as claimed in claim 1, wherein: The molar percentage of sodium propionate, glycine, polyvinyl pyrrolidone, methanol is sodium propionate 1mol%, glycine 15mol%, polyvinyl pyrrolidone 0.1mol%, methanol 50mol%.

4. The sodium propionate hydrate inhibitor for ensuring the flow of carbon dioxide transport pipelines as described in claim 1, characterized in that: The molar percentage of sodium propionate, glycine, polyvinyl pyrrolidone, methanol is sodium propionate 15mol%, glycine 1mol%, polyvinyl pyrrolidone 0.1mol%, methanol 50mol%.

5. The sodium propionate hydrate inhibitor for carbon dioxide pipeline flow assurance of claim 1, wherein: The molar percentage of sodium propionate, glycine, polyvinyl pyrrolidone, methanol is sodium propionate 1mol%, glycine 1mol%, polyvinyl pyrrolidone 1mol%, methanol 50mol%.

6. The sodium propionate hydrate inhibitor for carbon dioxide pipeline flow assurance of claim 1, wherein: The molar percentage of sodium propionate, glycine, polyvinyl pyrrolidone, methanol is sodium propionate 5mol%, glycine 8mol%, polyvinyl pyrrolidone 0.5mol%, methanol 5mol%.

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