A method of inhibiting coalescence of the decomposition process of a hydrate slurry

Abstract

The present application relates to natural gas safe storage and transportation technical field, disclose a kind of method for inhibiting hydrate slurry decomposition process coalescence.The method comprises: (1) hydrate decomposition stabilizer is added to hydrate slurry system, stirring;(2) temperature is raised to 1~2K below hydrate phase equilibrium temperature corresponding to system pressure and carries out first stage decomposition;(3) temperature is raised to 0.5~1K above hydrate phase equilibrium temperature corresponding to system pressure and carries out second stage decomposition;(4) the system temperature is increased by 1.8~2.2K and carries out third stage decomposition;(5) the system temperature is increased by 2.8~3.2K and carries out fourth stage decomposition;(6) the system temperature is raised to 298K above and hydrate is completely decomposed.The method is effectively regulated to the decomposition process of hydrate slurry by hydrate decomposition stabilizer and stage heating mode, inhibits the particle coalescence behavior caused by hydrate rapid decomposition, and then avoids to cause the situation of jam.

Description

Technical Field

[0001] The present invention relates to the technical field of safe storage and transportation of natural gas, and in particular to a method for inhibiting aggregation during the decomposition process of hydrate slurry. Background Art

[0002] With economic development, global energy demand continues to increase. Currently, the global demand for natural gas is growing faster than conventional energy sources such as oil and coal. Conventional CNG, LNG, and pipeline transportation methods have disadvantages such as high transmission pressure, low gas storage temperature, and high investment costs. Hydrate gas storage and transportation technology, as an emerging natural gas storage and transportation method, has great application prospects because 1 volume of hydrate can store 180 volumes of natural gas, the pressure required for hydrate storage and transportation is much lower than that of CNG, and hydrates are not easily explosive. However, the slow hydrate formation rate and low actual gas storage density seriously restrict the field application of hydrate technology.

[0003] Hydrate slurry gas storage technology based on oil-water emulsions has been gaining increasing attention in academia and industry in recent years. Oil-water emulsions are relatively stable mixtures formed by dispersing oil or water in the other phase with the help of an emulsifier. Because the water phase is dispersed in the oil phase as small droplets, the gas-liquid contact area increases, increasing the rate of hydrate formation and significantly increasing natural gas storage capacity. Furthermore, the generated solid hydrate particles, under the action of hydrate inhibitors, can be evenly dispersed in the oil phase, forming a hydrate slurry system with stable particles and good fluidity. After the hydrate slurry is transferred to its destination, the stored natural gas can be quickly recovered by decomposing it at elevated temperatures. However, in practical studies of this technology, the rapid decomposition rate of the hydrate slurry during rapid heating makes it difficult to effectively control. This can easily lead to blockage caused by particle aggregation during the decomposition process, which in turn affects the recovery and safe application of the technology. Therefore, how to ensure high gas storage capacity of hydrate slurry while effectively controlling the hydrate decomposition rate through appropriate physical or chemical methods to avoid aggregation behavior between particles during the decomposition process, but there are few reports on this aspect. Summary of the Invention

[0004] The purpose of the present invention is to overcome the problems in the prior art that the rapid heating method usually adopted makes the hydrate slurry decomposition process difficult to control, and the system blockage caused by particle aggregation is very likely to occur, resulting in the inability to effectively recover and utilize the stored natural gas. The present invention provides a method for inhibiting the aggregation of the hydrate slurry decomposition process. The method effectively controls the decomposition process of the hydrate slurry by adding a hydrate decomposition stabilizer and a staged heating method, thereby inhibiting the particle aggregation behavior caused by the rapid decomposition of the hydrate, thereby avoiding the occurrence of blockage.

[0005] To achieve the above object, the present application provides a method for inhibiting the coalescence of hydrate slurry decomposition process, which comprises the following steps:

[0006] (1) adding a hydrate decomposition stabilizer into a hydrate slurry system and stirring;

[0007] (2) raising the temperature to 1-2 K below the hydrate phase equilibrium temperature corresponding to the system pressure to perform the first stage decomposition;

[0008] (3) raising the temperature to 0.5-1 K above the hydrate phase equilibrium temperature corresponding to the system pressure to perform the second stage decomposition;

[0009] (4) continuously raising the system temperature by 1.8-2.2 K to perform the third stage decomposition;

[0010] (5) continuously raising the system temperature by 2.8-3.2 K to perform the fourth stage decomposition;

[0011] (6) raising the system temperature to above 298 K to completely decompose the hydrate.

[0012] Preferably, the hydrate decomposition stabilizer contains an alkyl glycoside compound and an alginic acid compound.

[0013] More preferably, the alkyl glycoside compound is selected from one or more than two of glucoside, dodecyl glucoside, dodecyl maltoside, dodecyl glucopyranoside and octyl glucopyranoside.

[0014] More preferably, the alginic acid compound is selected from one or more than two of alginic acid, sodium alginate, calcium alginate, magnesium alginate and methacrylated sodium alginate.

[0015] Preferably, the weight ratio of the alkyl glycoside compound to the alginic acid compound is 1:0.1-10, more preferably 1:0.2-5, and further preferably 1:0.2-2.

[0016] Preferably, the hydrate slurry is generated by reacting an oil-water system with a gas.

[0017] Preferably, the conditions for generating the hydrate slurry include a temperature of 273.2-283.2 K and a pressure of 0-10 MPa.

[0018] Preferably, the oil-water system contains a hydrate inhibitor, water and n-octane.

[0019] Preferably, the water content in the oil-water system is ≤20% by volume.

[0020] Preferably, the content of the hydrate inhibitor in the oil-water system is 0.8-1.5% by weight.

[0021] More preferably, the polymerization inhibitor is a surfactant, more preferably a non-ionic surfactant.

[0022] Preferably, the amount of the hydrate decomposition stabilizer is 0.05-1 wt%, preferably 0.3-0.8 wt% of the amount of water in the oil-water system.

[0023] Preferably, in step (1), the stirring time is ≥ 1 hour, more preferably 1.5-3 hours.

[0024] Preferably, the pressure of the system in steps (2) and (3) is 4300-4600 kPa.

[0025] Preferably, the hydrate phase equilibrium temperature is calculated using the Chen-Guo hydrate phase equilibrium model.

[0026] Preferably, in step (2), the heating rate of the heating is 3-5 K / h.

[0027] Preferably, in step (2), the time of the first stage decomposition is ≥ 1 hour, more preferably 1.5-2 hours.

[0028] Preferably, in step (3), the heating rate of the heating is 0.5-1 K / h.

[0029] Preferably, in step (3), the time of the second stage decomposition is ≥ 2 hours, more preferably 2.5-4 hours.

[0030] Preferably, in step (4), the heating rate of the heating is 0.5-1 K / h.

[0031] Preferably, in step (4), the time of the third stage decomposition is ≥ 3 hours, more preferably 3.5-5 hours.

[0032] Preferably, in step (5), the heating rate of the heating is 1-2 K / h.

[0033] Preferably, in step (5), the time of the fourth stage decomposition is ≥ 3 hours, more preferably 3.5-5 hours.

[0034] Preferably, in step (6), the heating rate can be 10-20 K / h.

[0035] Preferably, the average particle size of the hydrate particles in the hydrate slurry is 10-20 μm, preferably 15-17 μm.

[0036] The present invention provides a new method for inhibiting the aggregation of hydrate slurry during decomposition, aiming to solve the problem of excessively fast hydrate decomposition rate during rapid temperature increase, which leads to serious aggregation of particles and thus causes pipeline blockage. It provides new ideas for enriching the theory and industrial application of slurry hydrate gas storage technology, and is of great significance to the industrial application of new hydrate gas storage technology.

[0037] In a specific technical solution, the combination of the hydrate decomposition stabilizer and a staged temperature increase decomposition method effectively regulates the hydrate slurry decomposition process, preventing secondary coalescence between particles and ensuring safe and efficient recovery of stored natural gas. Preferably, the hydrate decomposition stabilizer comprises a blend of environmentally friendly biosurfactants. The staged temperature increase method slows the hydrate decomposition rate by gradually increasing the decomposition temperature, thereby controlling particle coalescence caused by the rapid temperature increase leading to the decomposition of large amounts of hydrates. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 It is the hydrate slurry generation and decomposition performance evaluation device of the present invention;

[0039] Figure 2 The temperature / pressure changes during the formation and decomposition of hydrate slurry in the oil-water system in Comparative Example 1;

[0040] Figure 3 This is a graph showing the change in average particle size during the formation and decomposition process of hydrate slurry in the oil-water system in Comparative Example 1;

[0041] Figure 4 This is the particle size distribution diagram of the oil-water system at different stages in Comparative Example 1;

[0042] Figures 5-9 This is a graph showing the mesoscopic evolution of particle size of the oil-water system in comparative example 1 at different stages.

[0043] Description of Reference Numerals

[0044] 1. Gas cylinder; 2. High-pressure reactor; 3. Low-temperature water bath jacket; 4. Stirring device; 5. Reaction zone; 6. Liquid discharge port; 7. Motor; 8. Temperature sensor; 9. High-precision microscopic measurement probe; 10. Pressure sensor; 11. Injection pump; 12. Data acquisition system. DETAILED DESCRIPTION

[0045] The following describes the specific embodiments of the present invention in detail with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present invention and are not intended to limit the present invention.

[0046] The endpoints of the ranges and any values ​​disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoints of each range, the endpoints of each range and individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered to be specifically disclosed herein.

[0047] The present invention provides a method for inhibiting aggregation during the decomposition process of a hydrate slurry, comprising the following steps:

[0048] (1) adding a hydrate decomposition stabilizer to the hydrate slurry system and stirring;

[0049] (2) The temperature is raised to 1-2 K below the hydrate phase equilibrium temperature corresponding to the system pressure to perform the first stage of decomposition;

[0050] (3) The temperature is raised to 0.5-1.0K above the hydrate phase equilibrium temperature corresponding to the system pressure to carry out the second stage of decomposition;

[0051] (4) The system temperature is further increased by 1.8 to 2.2 K to carry out the third stage of decomposition;

[0052] (5) The system temperature is further increased by 2.8 to 3.2 K to carry out the fourth stage of decomposition;

[0053] (6) Raise the system temperature to above 298K to completely decompose the hydrate.

[0054] The inventors discovered during their research that in order to solve the problem of excessively fast hydrate decomposition during the rapid heating and decomposition process of the hydrate slurry, which causes serious aggregation of particles and thus causes blockage of the pipeline, two measures need to be taken simultaneously during the hydrate decomposition process. One is to add a hydrate decomposition stabilizer to the hydrate slurry system before heating, and the other is to use a staged heating method to carry out a multi-stage decomposition process during the heating and decomposition process.

[0055] In the method described herein, a specific hydrate decomposition stabilizer is required to effectively inhibit severe particle aggregation during hydrate decomposition. The inventors have discovered that compounding the hydrate decomposition stabilizer with a specific environmentally friendly biosurfactant can better achieve the technical benefits described herein. In a preferred embodiment, the hydrate decomposition stabilizer comprises an alkyl glycoside compound and an alginic acid compound.

[0056] In a specific embodiment, the alkyl glycoside compound can be a conventional choice in the art, for example, the alkyl glycoside compound is selected from one or more of glucoside, dodecyl glucoside, dodecyl maltoside, dodecyl glucopyranoside, and octyl glucopyranoside. In a preferred embodiment, the alkyl glycoside compound is dodecyl glucoside or dodecyl glucopyranoside.

[0057] In a specific embodiment, the alginic acid compound can be a conventional choice in the art, for example, the alginic acid compound is selected from one or more of alginic acid, sodium alginate, calcium alginate, magnesium alginate and methacrylated sodium alginate. In a preferred embodiment, the alginic acid compound is sodium alginate.

[0058] In the method of the present invention, in order to improve the technical effect, the ratio of the amount of the alkyl glycoside compound to the alginic acid compound needs to be controlled within an appropriate range. In a preferred embodiment, the weight ratio of the alkyl glycoside compound to the alginic acid compound can be 1:0.1-10, more preferably 1:0.2-5, and even more preferably 1:0.2-2, for example, 1:0.2, 1:0.5, 1:0.8, 1:1, 1:1.2, 1:1.5, 1:1.8 or 1:2.

[0059] In this technical field, to facilitate the storage and transportation of gas (natural gas or a single pure gas within natural gas), the hydrate reaction liquid is reacted with gas to produce a stable hydrate slurry. The gas is then recovered by heating upon arrival at the destination. The method of the present invention is applicable to hydrate reaction liquids commonly found in the art, and is particularly applicable to oil-water systems. Specifically, in the preferred embodiment of the present invention, the hydrate slurry is produced by reacting an oil-water system with gas. In the method of the present invention, the oil in the oil-water system refers to an organic substance, preferably n-octane.

[0060] In a preferred embodiment, the conditions for generating the hydrate slurry include: a temperature of 273.2 to 283.2 K, for example, 273.2 K, 274.7 K, 275.6 K, 277.5 K, 278.3 K, 279.6 K, 280.4 K, 281.5 K, 282.3 K or 283.2 K; and a pressure of 0 to 10 MPa, for example, 0 MP, 0.5 MP, 1 MP, 2 MP, 3 MP, 4 MP, 5 MP, 5.8 MP, 6.5 MP, 7 MP, 8 MP, 9 MP or 10 MP.

[0061] In a specific embodiment of the present invention, the oil-water system (hydrate reaction liquid) contains a hydrate inhibitor, water, and n-octane. The inhibitor is a surfactant commonly used in the art, preferably one or more nonionic surfactants. For example, the inhibitor is a combination of two nonionic surfactants: Span 20 (sorbitan monolaurate) and Tween 80 (sorbitan monooleate polyoxyethylene ether), with the weight ratio of Span 20 to Tween 80 being 1:1.

[0062] In a specific embodiment, the content of the hydrate inhibitor in the oil-water system can be 0.8 to 1.5 weight%, for example, 0.8 weight%, 0.9 weight%, 1 weight%, 1.1 weight%, 1.2 weight%, 1.3 weight%, 1.4 weight% or 1.5 weight%.

[0063] In a preferred embodiment, the water content of the oil-water system is ≤20% by volume. In a more preferred embodiment, the water content of the oil-water system is 5-10% by volume. In this context, the water content refers to the ratio of the volume of water to the total volume of water and organic matter in the oil-water system.

[0064] In the method of the present invention, in order to better achieve the technical effects described in this application, it is necessary to reasonably control the amount of the hydrate decomposition stabilizer.

[0065] In a specific embodiment, the amount of the hydrate decomposing stabilizer can be 0.05-1% by weight of the amount of water in the oil-water system. In a preferred embodiment, the amount of the hydrate decomposing stabilizer is 0.3-0.8% by weight, for example, 0.3%, 0.4%, 0.5%, 0.6%, 0.7% or 0.8% by weight.

[0066] In the method of the present invention, the hydrate decomposition stabilizer is added before the temperature is raised to decompose the hydrate. In order to ensure that the hydrate decomposition stabilizer is evenly dispersed in the entire system, it is necessary to continue stirring for a period of time after adding the hydrate decomposition stabilizer. In a specific embodiment, in step (1), the stirring time is ≥ 1 hour. In a preferred embodiment, the stirring time is 1.5 to 3 hours, for example, 1.5 hours, 2 hours, 2.5 hours or 3 hours.

[0067] In the method of the present invention, the system pressure in step (2) and step (3) can be 4300-4600 kPa, for example, 4300 kPa, 4350 kPa, 4380 kPa, 4400 kPa, 4438 kPa, 4450 kPa, 4500 kPa, 4528 kPa, 4550 kPa or 4600 kPa.

[0068] In a specific embodiment, the hydrate phase equilibrium temperature can be calculated using the Chen-Guo hydrate phase equilibrium model.

[0069] In the method of the present invention, step (2) needs to be quickly heated to the target temperature. In a specific embodiment, in step (2), the heating rate of the heating can be 3 to 5K / h, for example, 3K / h, 3.5K / h, 4K / h, 4.5K / h or 5K / h. In a specific embodiment, in step (2), the temperature can be raised to 1K, 1.2K, 1.4K, 1.5K, 1.8K or 2K below the hydrate phase equilibrium temperature corresponding to the system pressure. After heating to the target temperature, it is necessary to maintain it for a period of time for the first stage decomposition. In a specific embodiment, in step (2), the time for the first stage decomposition is ≥1 hour, preferably 1.5 to 2 hours.

[0070] In the method of the present invention, the slow heating in step (3) and step (4) requires slowly heating to the target temperature.

[0071] In a specific embodiment, in step (3), the heating rate of the heating can be 0.5 to 1 K / h, for example, 0.5 K / h, 0.6 K / h, 0.7 K / h, 0.8 K / h, 0.9 K / h or 1 K / h. In a specific embodiment, in step (3), the temperature can be raised to 0.5 K, 0.6 K, 0.7 K, 0.8 K, 0.9 K or 1 K above the hydrate phase equilibrium temperature corresponding to the system pressure. After heating to the target temperature, it is necessary to maintain it for a period of time for the second stage decomposition. In a specific embodiment, in step (3), the time for the second stage decomposition is ≥ 2 hours, preferably 2.5 to 4 hours, for example 2.5 hours, 3 hours, 3.5 hours or 4 hours.

[0072] In a specific embodiment, in step (4), the heating rate of the heating can be 0.5 to 1 K / h, for example, 0.5 K / h, 0.6 K / h, 0.7 K / h, 0.8 K / h, 0.9 K / h or 1 K / h. In a specific embodiment, in step (4), the system temperature can be further increased by 1.8 K, 1.9 K, 2 K, 2.1 K or 2.2 K to perform the third stage decomposition. After heating to the target temperature, it is necessary to maintain it for a period of time for the third stage decomposition. In a specific embodiment, in step (4), the time for the third stage decomposition is ≥ 3 hours, preferably 3.5 to 5 hours, for example 3.5 hours, 4 hours, 4.5 hours or 5 hours.

[0073] In the method of the present invention, step (5) needs to slowly heat up to the target temperature. In a specific embodiment, in step (5), the heating rate of the heating can be 1 to 2K / h, for example, 1K / h, 1.5K / h or 2K / h. In a specific embodiment, the system temperature can be further increased by 2.8K, 2.9K, 3K, 3.1K or 3.2K to carry out the fourth stage decomposition. After heating to the target temperature, it is necessary to maintain it for a period of time for the fourth stage decomposition. In a specific embodiment, in step (5), the time for the fourth stage decomposition is ≥3 hours, preferably 3.5 to 5 hours, for example, 3.5 hours, 4 hours, 4.5 hours or 5 hours.

[0074] In the present invention, after step (5) is completed, the hydrate decomposition in the system is observed. After the hydrates in the system are substantially decomposed, the system temperature is rapidly raised to above 298K to completely decompose the remaining hydrates. The degree of substantial completion of the hydrate decomposition in step (5) is determined by the mesoscopic morphology and average particle size of the particles in the system. When the mesoscopic morphology of the system presents a uniform emulsion state and the average particle size of the particles tends to be stable, the hydrate decomposition process is considered to be substantially complete.

[0075] In a specific embodiment, in step (6), the heating rate can be 10 to 20 K / h.

[0076] In the present invention, the generation and decomposition processes of the hydrate slurry are both carried out in the hydrate slurry generation and decomposition performance evaluation device. Figure 1As shown, the evaluation device includes a gas cylinder 1, a high-pressure reactor 2, a low-temperature water bath jacket 3, a stirring device 4, a reaction zone 5, a drain port 6, a motor 7, a temperature sensor 8, a high-precision microscopic measurement probe 9, a pressure sensor 10, an injection pump 11, and a data acquisition system 12. The gas cylinder 1 is used to supply gas to the high-pressure reactor 2, and the high-pressure reactor 2 is used to generate and decompose the hydrate slurry. The low-temperature water bath jacket 3 is used to adjust the temperature of the high-pressure reactor 2. The stirring device 4 is used to strengthen the gas-liquid reaction in generating the hydrate slurry. The reaction zone 5 is the place where the hydrate slurry is generated and decomposed. The drain port The port 6 is used to discharge the liquid in the high-pressure reactor 2. The motor 7 is used to supply power to the device. The temperature sensor 8 is used to collect the temperature of the reaction zone 5 online. The high-precision microscopic measurement probe 9 is used to record the particle size distribution and average particle size of the particles in the system during the generation and decomposition of the hydrate slurry online. The pressure sensor 10 is used to collect the system pressure during the generation and decomposition of the hydrate slurry online. The injection pump 11 is used to quantitatively inject the hydrate decomposition stabilizer into the high-pressure reactor 2 under pressure. The data acquisition system 12 is used to record and preserve the temperature, pressure, average particle size, particle size distribution, and mesoscopic morphological evolution of the system during the generation and decomposition of the hydrate slurry.

[0077] In a specific embodiment of the present invention, the Figure 1 The evaluation device shown has an effective volume of 635 mL, a design pressure of 25 MPa, and a design temperature range of 253 to 323 K. The hydrate slurry generation and decomposition evaluation process specifically includes:

[0078] 1) Adding the hydrate reaction solution (oil-water system) required for the experiment into the autoclave 2, regulating the temperature in the autoclave 2 by the low-temperature water bath jacket 3, and collecting the temperature of the reaction zone 5 online by the temperature sensor 8;

[0079] 2) Setting the experimental temperature, injecting high-pressure gas into the autoclave 2 through the gas cylinder 1 to the required experimental pressure, and turning on the stirring device 4 to intensify the gas-liquid reaction until a stable hydrate slurry is formed in the system. During the experiment, the system pressure is collected online by the pressure sensor 10;

[0080] 3) After the hydrate slurry is stabilized, the hydrate decomposition stabilizer required for the experiment is quantitatively injected into the high-pressure reactor 2 under pressure via the injection pump 11. The hydrate decomposition experiment temperature can be controlled by the low-temperature water bath jacket 3. During the experiment, the particle size distribution and average particle size in the system are recorded online by a high-precision microscopic measurement probe 9;

[0081] 4) After the hydrate decomposition reaction is completed, the liquid in the autoclave 2 is discharged through the drain port 6.

[0082] The present invention also provides a method for determining whether particle aggregation occurs during the decomposition process of a hydrate slurry, namely, characterizing the process by changing the average particle size of the system during the decomposition process. Compared with the average particle size of the particles in the initial system of a uniform and stable hydrate slurry, if the average particle size of the particles in the system gradually decreases during the temperature increase decomposition process and does not exceed the initial particle size of the hydrate slurry, it is considered that no aggregation occurs during the decomposition process of the hydrate slurry; if the average particle size of the particles in the system during the decomposition process becomes larger than the initial particle size of the hydrate slurry, it is considered that aggregation occurs during the decomposition process of the hydrate slurry.

[0083] In the present invention, the average particle size of the hydrate particles in the hydrate slurry is 10-20 μm, preferably 15-17 μm, for example, 15 μm, 15.5 μm, 15.8 μm, 16 μm, 16.5 μm, 16.8 μm or 17 μm.

[0084] The present invention will be described in detail below through examples, but the protection scope of the present invention is not limited thereto.

[0085] The following examples and comparative examples were carried out in the hydrate slurry generation and decomposition performance evaluation device of the present invention. Figure 1 As shown, the evaluation device includes a gas cylinder 1, a high-pressure reactor 2, a low-temperature water bath jacket 3, a stirring device 4, a reaction zone 5, a drain port 6, a motor 7, a temperature sensor 8, a high-precision microscopic measurement probe 9, a pressure sensor 10, an injection pump 11, and a data acquisition system 12. The gas cylinder 1 is used to supply gas to the high-pressure reactor 2, and the high-pressure reactor 2 is used to generate and decompose the hydrate slurry. The low-temperature water bath jacket 3 is used to adjust the temperature of the high-pressure reactor 2. The stirring device 4 is used to strengthen the gas-liquid reaction in generating the hydrate slurry. The reaction zone 5 is the place where the hydrate slurry is generated and decomposed. The drain port The port 6 is used to discharge the liquid in the high-pressure reactor 2. The motor 7 is used to supply power to the device. The temperature sensor 8 is used to collect the temperature of the reaction zone 5 online. The high-precision microscopic measurement probe 9 is used to record the particle size distribution and average particle size of the particles in the system during the generation and decomposition of the hydrate slurry online. The pressure sensor 10 is used to collect the system pressure during the generation and decomposition of the hydrate slurry online. The injection pump 11 is used to quantitatively inject the hydrate decomposition stabilizer into the high-pressure reactor 2 under pressure. The data acquisition system 12 is used to record and preserve the temperature, pressure, average particle size, particle size distribution, and mesoscopic morphological evolution of the system during the generation and decomposition of the hydrate slurry.

[0086] Example 1

[0087] In this example, the hydrate reaction solution consisted of an oil-water system (n-octane + water + hydrate inhibitor) containing 1 wt% hydrate inhibitor and a water content of 10% by volume. The test gas was pure methane, and the hydrate inhibitor was a nonionic surfactant composed of Span 20 and Tween 80 in a 1:1 weight ratio. The experimental temperature for hydrate slurry formation was 274.7 K and the experimental pressure was 5.8 MPa.

[0088] In the step (1), the hydrate decomposition stabilizer is composed of dodecyl glucoside and sodium alginate in a weight ratio of 1:1, and the amount of the hydrate decomposition stabilizer added is 0.5% by weight of the water content in the hydrate reaction solution.

[0089] The specific steps for generating hydrate slurry are:

[0090] S1, adding 250 mL of an oil-water system (n-octane + water + hydrate inhibitor) containing 1 wt% hydrate inhibitor and a water content of 10% by volume into autoclave 2;

[0091] S2. The temperature of the autoclave 2 is set to 274.7 K, and methane gas is introduced into the autoclave 2 through the gas cylinder 1 to a pressure of 5.8 MPa. As the temperature of the autoclave 2 decreases, hydrate particles begin to appear in the system. After continuous reaction, a stable hydrate slurry is obtained.

[0092] The specific steps of hydrate slurry decomposition are:

[0093] (1) After the hydrate slurry is formed and stabilized, the system pressure is 4526 kPa. The hydrate formation temperature is calculated to be 278.7 K using the Chen-Guo hydrate phase equilibrium model. A hydrate decomposition stabilizer is added to the hydrate slurry system under constant pressure through the injection pump 11, and the mixture is stirred for 1.5 h to ensure that the hydrate decomposition stabilizer is evenly dispersed in the entire system.

[0094] (2) Rapidly increase the experimental temperature at a heating rate of 4 K / h to 1 K below the hydrate phase equilibrium temperature corresponding to the system pressure (i.e., 277.7 K), and maintain the temperature for 1.5 h after stabilization;

[0095] (3) Slowly increase the experimental temperature at a heating rate of 0.8 K / h to 0.5 K above the hydrate phase equilibrium temperature corresponding to the system pressure (i.e., 279.2 K), and maintain the temperature for 3 h after stabilization;

[0096] (4) The experimental temperature was slowly increased by 2 K (i.e., 281.2 K) at a heating rate of 0.8 K / h, and maintained for 4 h after the temperature stabilized;

[0097] (5) The experimental temperature was slowly increased by 3.0 K (i.e., 284.2 K) at a heating rate of 1.5 K / h. After the temperature stabilized, it was maintained for 4 h. The hydrate decomposition in the system was observed, and the hydrate decomposition was basically completed.

[0098] (6) Rapidly increase the temperature to above 298 K at a heating rate of 15 K / h to completely decompose the remaining hydrates.

[0099] The temperature, pressure, average particle size, particle size distribution, and mesoscopic morphology evolution during the experiment were recorded and stored by a data acquisition system. Table 2 details the changes in average particle size and particle aggregation during the formation and decomposition of the hydrate slurry.

[0100] Example 2

[0101] In this embodiment, the hydrate reaction liquid is an oil-water system (n-octane + water + hydrate inhibitor) containing 1% by weight of a hydrate inhibitor and a water content of 10% by volume. The experimental test gas is pure methane gas, and the hydrate inhibitor is a nonionic surfactant composed of Span20 and Tween80 in a weight ratio of 1:1. The experimental temperature for hydrate slurry generation is 274.7K and the experimental pressure is 5.8MPa. In step (1), the hydrate decomposition stabilizer is composed of dodecyl glucoside and sodium alginate in a weight ratio of 1:2, and the amount of hydrate decomposition stabilizer added is 0.5% by weight of the water content in the hydrate reaction liquid.

[0102] The specific steps for generating hydrate slurry are:

[0103] S1, adding 250 mL of an oil-water system (n-octane + water + hydrate inhibitor) containing 1 wt% hydrate inhibitor and a water content of 10% by volume into autoclave 2;

[0104] S2. The temperature of the autoclave 2 is set to 274.7 K, and methane gas is introduced into the autoclave 2 through the gas cylinder 1 to a pressure of 5.8 MPa. As the temperature of the autoclave 2 decreases, hydrate particles begin to appear in the system. After continuous reaction, a stable hydrate slurry is obtained.

[0105] The specific steps of hydrate slurry decomposition are:

[0106] (1) After the hydrate slurry is formed and stabilized, the system pressure is 4558 kPa. The hydrate formation temperature is calculated to be 278.7 K using the Chen-Guo hydrate phase equilibrium model. A hydrate decomposition stabilizer is added to the hydrate slurry system under constant pressure through the injection pump 11, and the mixture is stirred for 1.5 h to ensure that the hydrate decomposition stabilizer is evenly dispersed in the entire system.

[0107] (2) Rapidly increase the experimental temperature at a heating rate of 4 K / h to 1 K below the hydrate phase equilibrium temperature corresponding to the system pressure (i.e., 277.7 K), and maintain the temperature for 1.5 h after stabilization;

[0108] (3) Slowly increase the experimental temperature at a heating rate of 0.8 K / h to 0.5 K above the hydrate phase equilibrium temperature corresponding to the system pressure (i.e., 279.2 K), and maintain the temperature for 3 h after stabilization;

[0109] (4) The experimental temperature was slowly increased by 2 K (i.e., 281.2 K) at a heating rate of 0.8 K / h, and maintained for 4 h after the temperature stabilized;

[0110] (5) The experimental temperature was slowly increased by 3.0 K (i.e., 284.2 K) at a heating rate of 1.5 K / h. After the temperature stabilized, it was maintained for 4 h. The hydrate decomposition in the system was observed, and the hydrate decomposition was basically completed.

[0111] (6) Rapidly increase the temperature to above 298 K at a heating rate of 15 K / h to completely decompose the remaining hydrates.

[0112] The temperature, pressure, average particle size, particle size distribution, and mesoscopic morphology evolution during the experiment were recorded and stored by a data acquisition system 12. The changes in average particle size within the system and whether particles coalesced during the formation and decomposition of the hydrate slurry are detailed in Table 2.

[0113] Example 3

[0114] In this embodiment, the hydrate reaction liquid is an oil-water system (n-octane + water + hydrate inhibitor) containing 1% by weight of a hydrate inhibitor and a water content of 10% by volume. The experimental test gas is pure methane gas, and the hydrate inhibitor is a nonionic surfactant composed of Span20 and Tween80 in a weight ratio of 1:1. The experimental temperature for hydrate slurry generation is 274.7K and the experimental pressure is 5.8MPa. In step (1), the hydrate decomposition stabilizer is composed of dodecyl glucoside and sodium alginate in a weight ratio of 1:0.2, and the amount of hydrate decomposition stabilizer added is 0.5% by weight of the water content in the hydrate reaction liquid.

[0115] The specific steps for generating hydrate slurry are:

[0116] S1, adding 250 mL of an oil-water system (n-octane + water + hydrate inhibitor) containing 1 wt% hydrate inhibitor and a water content of 10% by volume into autoclave 2;

[0117] S2, set the temperature of the high-pressure reactor 2 to 274.7 K, and introduce methane gas into the high-pressure reactor 2 through the gas cylinder 1 to 5.8 MPa. As the temperature of the high-pressure reactor 2 decreases, hydrate particles begin to appear in the system. After continuous reaction, stable hydrate slurry is obtained.

[0118] The specific steps of hydrate slurry decomposition are as follows:

[0119] (1) After the hydrate slurry is generated stably, the system pressure is 4512 kPa. The hydrate formation temperature at this time is calculated to be 278.7 K by using the Chen-Guo hydrate phase equilibrium model. The hydrate decomposition stabilizer is added to the hydrate slurry system under constant pressure through the injection pump 11, and the stirring is continued for 1.5 h to ensure that the hydrate decomposition stabilizer is uniformly dispersed in the whole system.

[0120] (2) The experimental temperature is quickly raised to 1.5 K (i.e. 277.2 K) below the hydrate phase equilibrium temperature corresponding to the system pressure at a rate of 4 K / h. After the temperature is stable for 1.5 h;

[0121] (3) The experimental temperature is slowly raised to 0.5 K (i.e. 279.2 K) above the hydrate phase equilibrium temperature corresponding to the system pressure at a rate of 0.8 K / h. After the temperature is stable for 3 h;

[0122] (4) The experimental temperature is continuously slowly raised by 2 K (i.e. 281.2 K) at a rate of 0.8 K / h. After the temperature is stable for 4 h;

[0123] (5) The experimental temperature is continuously slowly raised by 3.0 K (i.e. 284.2 K) at a rate of 1.5 K / h. After the temperature is stable for 4 h, the hydrate decomposition is observed, and the hydrate decomposition is basically completed;

[0124] (6) The remaining hydrate is completely decomposed by quickly raising the temperature to above 298 K at a rate of 15 K / h.

[0125] The temperature, pressure, average particle size, particle size distribution, and mesoscopic morphology evolution during the experiment are recorded and saved by the data acquisition system 12. The changes in the average particle size in the system and whether the particles are aggregated during the generation and decomposition of the hydrate slurry are shown in Table 2.

[0126] Example 4

[0127] In this embodiment, the hydrate reaction liquid is an oil-water system (n-octane + water + hydrate inhibitor) containing 1% by weight of a hydrate inhibitor and a water content of 10% by volume. The experimental test gas is pure methane gas, and the hydrate inhibitor is a nonionic surfactant composed of Span 20 and Tween 80 in a weight ratio of 1:1. The experimental temperature for hydrate slurry generation is 274.7K and the experimental pressure is 5.8MPa. In step (1), the hydrate decomposition stabilizer is composed of dodecylpyranoside and sodium alginate in a weight ratio of 1:1, and the amount of hydrate decomposition stabilizer added is 0.5% by weight of the water content in the hydrate reaction liquid.

[0128] The specific steps for generating hydrate slurry are:

[0129] S1, adding 250 mL of an oil-water system (n-octane + water + hydrate inhibitor) containing 1 wt% hydrate inhibitor and a water content of 10% by volume into autoclave 2;

[0130] S2. The temperature of the autoclave 2 is set to 274.7 K, and methane gas is introduced into the autoclave 2 through the gas cylinder 1 to a pressure of 5.8 MPa. As the temperature of the autoclave 2 decreases, hydrate particles begin to appear in the system. After continuous reaction, a stable hydrate slurry is obtained.

[0131] The specific steps of hydrate slurry decomposition are:

[0132] (1) After the hydrate slurry is formed and stabilized, the system pressure is 4506 kPa. The hydrate formation temperature is calculated to be 278.7 K using the Chen-Guo hydrate phase equilibrium model. A hydrate decomposition stabilizer is added to the hydrate slurry system under constant pressure through the injection pump 11, and the mixture is stirred for 1.5 h to ensure that the hydrate decomposition stabilizer is evenly dispersed in the entire system.

[0133] (2) Rapidly increase the experimental temperature at a heating rate of 4 K / h to 1.5 K below the hydrate phase equilibrium temperature corresponding to the system pressure (i.e., 277.2 K), and maintain the temperature for 1.5 h after stabilization;

[0134] (3) Slowly increase the experimental temperature at a heating rate of 0.8 K / h to 0.5 K above the hydrate phase equilibrium temperature corresponding to the system pressure (i.e., 279.2 K), and maintain the temperature for 3 h after stabilization;

[0135] (4) The experimental temperature was slowly increased by 2 K (i.e., 281.2 K) at a heating rate of 0.8 K / h, and maintained for 4 h after the temperature stabilized;

[0136] (5) The experimental temperature was slowly increased by 3.0 K (i.e., 284.2 K) at a heating rate of 1.5 K / h. After the temperature stabilized, it was maintained for 4 h. The hydrate decomposition in the system was observed, and the hydrate decomposition was basically completed.

[0137] (6) Rapidly increase the temperature to above 298 K at a heating rate of 15 K / h to completely decompose the remaining hydrates.

[0138] The temperature, pressure, average particle size, particle size distribution, and mesoscopic morphology evolution during the experiment were recorded and stored by a data acquisition system 12. The changes in average particle size within the system and whether particles coalesced during the formation and decomposition of the hydrate slurry are detailed in Table 2.

[0139] Example 5

[0140] In this embodiment, the hydrate reaction liquid is an oil-water system (n-octane + water + hydrate inhibitor) containing 1% by weight of a hydrate inhibitor and a water content of 10% by volume. The experimental test gas is pure methane gas, and the hydrate inhibitor is a nonionic surfactant composed of Span20 and Tween80 in a weight ratio of 1:1. The experimental temperature for hydrate slurry generation is 274.7K and the experimental pressure is 5.8MPa. In step (1), the hydrate decomposition stabilizer is composed of dodecyl glucoside and sodium alginate in a weight ratio of 1:1, and the amount of hydrate decomposition stabilizer added is 0.5% by weight of the water content in the hydrate reaction liquid.

[0141] The specific steps for generating hydrate slurry are:

[0142] S1, adding 250 mL of an oil-water system (n-octane + water + hydrate inhibitor) containing 1 wt% hydrate inhibitor and a water content of 10% by volume into autoclave 2;

[0143] S2. The temperature of the autoclave 2 is set to 274.7 K, and methane gas is introduced into the autoclave 2 through the gas cylinder 1 to a pressure of 5.8 MPa. As the temperature of the autoclave 2 decreases, hydrate particles begin to appear in the system. After continuous reaction, a stable hydrate slurry is obtained.

[0144] The specific steps of hydrate slurry decomposition are:

[0145] (1) After the hydrate slurry is formed and stabilized, the system pressure is 4532 kPa. The hydrate formation temperature is calculated to be 278.7 K using the Chen-Guo hydrate phase equilibrium model. A hydrate decomposition stabilizer is added to the hydrate slurry system under constant pressure through the injection pump 11, and the mixture is stirred for 2 h to ensure that the hydrate decomposition stabilizer is evenly dispersed in the entire system.

[0146] (2) Rapidly increase the experimental temperature at a heating rate of 3 K / h to 1.5 K below the hydrate phase equilibrium temperature corresponding to the system pressure (i.e., 277.2 K), and maintain the temperature for 1.5 h after stabilization;

[0147] (3) Slowly increase the experimental temperature at a heating rate of 0.7 K / h to 0.5 K above the hydrate phase equilibrium temperature corresponding to the system pressure (i.e., 279.2 K), and maintain the temperature for 3 h after stabilization;

[0148] (4) The experimental temperature was slowly increased by 2 K (i.e., 281.2 K) at a heating rate of 0.7 K / h, and maintained for 5 h after the temperature stabilized;

[0149] (5) The experimental temperature was slowly increased by 3.0 K (i.e., 284.2 K) at a heating rate of 1.5 K / h. After the temperature stabilized, it was maintained for 4 h. The hydrate decomposition in the system was observed, and the hydrate decomposition was basically completed.

[0150] (6) Rapidly increase the temperature to above 298 K at a heating rate of 15 K / h to completely decompose the remaining hydrates.

[0151] The temperature, pressure, average particle size, particle size distribution, and mesoscopic morphology evolution during the experiment were recorded and stored by a data acquisition system 12. The changes in average particle size within the system and whether particles coalesced during the formation and decomposition of the hydrate slurry are detailed in Table 2.

[0152] Example 6

[0153] In this embodiment, the hydrate reaction liquid is an oil-water system (n-octane + water + hydrate inhibitor) containing 1% by weight of a hydrate inhibitor and a water content of 10% by volume. The experimental test gas is pure methane gas, and the hydrate inhibitor is a nonionic surfactant composed of Span20 and Tween80 in a weight ratio of 1:1. The experimental temperature for hydrate slurry generation is 274.7K and the experimental pressure is 5.8MPa. In step (1), the hydrate decomposition stabilizer is composed of dodecyl glucoside and sodium alginate in a weight ratio of 1:0.5, and the amount of hydrate decomposition stabilizer added is 0.5% by weight of the water content in the hydrate reaction liquid.

[0154] The specific steps for generating hydrate slurry are:

[0155] S1, adding 250 mL of an oil-water system (n-octane + water + hydrate inhibitor) containing 1 wt% hydrate inhibitor and a water content of 10% by volume into autoclave 2;

[0156] S2. The temperature of the autoclave 2 is set to 274.7 K, and methane gas is introduced into the autoclave 2 through the gas cylinder 1 to a pressure of 5.8 MPa. As the temperature of the autoclave 2 decreases, hydrate particles begin to appear in the system. After continuous reaction, a stable hydrate slurry is obtained.

[0157] The specific steps of hydrate slurry decomposition are:

[0158] (1) After the hydrate slurry is formed and stabilized, the system pressure is 4508 kPa. The hydrate formation temperature is calculated to be 278.7 K using the Chen-Guo hydrate phase equilibrium model. A hydrate decomposition stabilizer is added to the hydrate slurry system under constant pressure through the injection pump 11, and the mixture is stirred for 1.5 h to ensure that the hydrate decomposition stabilizer is evenly dispersed in the entire system.

[0159] (2) Rapidly increase the experimental temperature at a heating rate of 3 K / h to 1.5 K below the hydrate phase equilibrium temperature corresponding to the system pressure (i.e., 277.2 K), and maintain the temperature for 1.5 h after stabilization;

[0160] (3) Slowly increase the experimental temperature at a heating rate of 0.7 K / h to 0.5 K above the hydrate phase equilibrium temperature corresponding to the system pressure (i.e., 279.2 K), and maintain the temperature for 3 h after stabilization;

[0161] (4) The experimental temperature was slowly increased by 2 K (i.e., 281.2 K) at a heating rate of 0.7 K / h, and maintained for 4 h after the temperature stabilized;

[0162] (5) The experimental temperature was slowly increased by 3.0 K (i.e., 284.2 K) at a heating rate of 1.5 K / h. After the temperature stabilized, it was maintained for 4 h. The hydrate decomposition in the system was observed, and the hydrate decomposition was basically completed.

[0163] (6) Rapidly increase the temperature to above 298 K at a heating rate of 15 K / h to completely decompose the remaining hydrates.

[0164] The temperature, pressure, average particle size, particle size distribution, and mesoscopic morphology evolution during the experiment were recorded and stored by a data acquisition system 12. The changes in average particle size within the system and whether particles coalesced during the formation and decomposition of the hydrate slurry are detailed in Table 2.

[0165] Example 7

[0166] In this embodiment, the hydrate reaction liquid is an oil-water system (n-octane + water + hydrate inhibitor) containing 1% by weight of a hydrate inhibitor and a water content of 10% by volume. The experimental test gas is pure methane gas, and the hydrate inhibitor is a nonionic surfactant composed of Span20 and Tween80 in a weight ratio of 1:1. The experimental temperature for hydrate slurry generation is 274.7K and the experimental pressure is 5.8MPa. In step (1), the hydrate decomposition stabilizer is composed of dodecyl glucoside and sodium alginate in a weight ratio of 1:2, and the amount of hydrate decomposition stabilizer added is 0.8% by weight of the water content in the hydrate reaction liquid.

[0167] The specific steps for generating hydrate slurry are:

[0168] S1, adding 250 mL of an oil-water system (n-octane + water + hydrate inhibitor) containing 1 wt% hydrate inhibitor and a water content of 10% by volume into autoclave 2;

[0169] S2. The temperature of the autoclave 2 is set to 274.7 K, and methane gas is introduced into the autoclave 2 through the gas cylinder 1 to a pressure of 5.8 MPa. As the temperature of the autoclave 2 decreases, hydrate particles begin to appear in the system. After continuous reaction, a stable hydrate slurry is obtained.

[0170] The specific steps of hydrate slurry decomposition are:

[0171] (1) After the hydrate slurry is formed and stabilized, the system pressure is 4538 kPa. The hydrate formation temperature is calculated to be 278.7 K using the Chen-Guo hydrate phase equilibrium model. A hydrate decomposition stabilizer is added to the hydrate slurry system under constant pressure through the injection pump 11, and the mixture is stirred for 1.5 h to ensure that the hydrate decomposition stabilizer is evenly dispersed in the entire system.

[0172] (2) Rapidly increase the experimental temperature at a heating rate of 3 K / h to 1.5 K below the hydrate phase equilibrium temperature corresponding to the system pressure (i.e., 277.2 K), and maintain the temperature for 1.5 h after stabilization;

[0173] (3) Slowly increase the experimental temperature at a heating rate of 0.7 K / h to 0.5 K above the hydrate phase equilibrium temperature corresponding to the system pressure (i.e., 279.2 K), and maintain the temperature for 3 h after stabilization;

[0174] (4) The experimental temperature was slowly increased by 2 K (i.e., 281.2 K) at a heating rate of 0.7 K / h, and maintained for 4 h after the temperature stabilized;

[0175] (5) The experimental temperature was slowly increased by 3.0 K (i.e., 284.2 K) at a heating rate of 1.5 K / h. After the temperature stabilized, it was maintained for 4 h. The hydrate decomposition in the system was observed, and the hydrate decomposition was basically completed.

[0176] (6) Rapidly increase the temperature to above 298 K at a heating rate of 15 K / h to completely decompose the remaining hydrates.

[0177] The temperature, pressure, average particle size, particle size distribution, and mesoscopic morphology evolution during the experiment were recorded and stored by a data acquisition system 12. The changes in average particle size within the system and whether particles coalesced during the formation and decomposition of the hydrate slurry are detailed in Table 2.

[0178] Example 8

[0179] In this embodiment, the hydrate reaction liquid is an oil-water system (n-octane + water + hydrate inhibitor) containing 1% by weight of a hydrate inhibitor and a water content of 5% by volume. The experimental test gas is pure methane gas, and the hydrate inhibitor is a nonionic surfactant composed of Span20 and Tween80 in a weight ratio of 1:1. The experimental temperature for hydrate slurry generation is 274.7K and the experimental pressure is 5.8MPa. In step (1), the hydrate decomposition stabilizer is composed of dodecyl glucoside and sodium alginate in a weight ratio of 1:1, and the amount of hydrate decomposition stabilizer added is 0.5% by weight of the water content in the hydrate reaction liquid.

[0180] The specific steps for generating hydrate slurry are:

[0181] S1, adding 250 mL of an oil-water system (n-octane + water + hydrate inhibitor) containing 1 wt% hydrate inhibitor and a water content of 5 vol% into autoclave 2;

[0182] S2. The temperature of the autoclave 2 is set to 274.7 K, and methane gas is introduced into the autoclave 2 through the gas cylinder 1 to a pressure of 5.8 MPa. As the temperature of the autoclave 2 decreases, hydrate particles begin to appear in the system. After continuous reaction, a stable hydrate slurry is obtained.

[0183] The specific steps of hydrate slurry decomposition are:

[0184] (1) After the hydrate slurry is formed and stabilized, the system pressure is 4520 kPa. The hydrate formation temperature is calculated to be 278.7 K using the Chen-Guo hydrate phase equilibrium model. A hydrate decomposition stabilizer is added to the hydrate slurry system under constant pressure through the injection pump 11, and the mixture is stirred for 1.5 h to ensure that the hydrate decomposition stabilizer is evenly dispersed in the entire system.

[0185] (2) The experimental temperature is rapidly increased to 1.5K below the hydrate phase equilibrium temperature corresponding to the system pressure (i.e. 277.2K) at a heating rate of 4K / h, and the temperature is kept stable for 1.5h;

[0186] (3) The experimental temperature is slowly increased to 0.5K above the hydrate phase equilibrium temperature corresponding to the system pressure (i.e. 279.2K) at a heating rate of 0.8K / h, and the temperature is kept stable for 3h;

[0187] (4) The experimental temperature is continuously slowly increased by 2K (i.e. 281.2K) at a heating rate of 0.8K / h, and the temperature is kept stable for 4h;

[0188] (5) The experimental temperature is continuously slowly increased by 3.0K (i.e. 284.2K) at a heating rate of 1.5K / h, and the temperature is kept stable for 4h, and the hydrate decomposition in the system is observed, and the hydrate decomposition is basically completed;

[0189] (6) The remaining hydrate is completely decomposed by rapidly increasing the temperature to above 298K at a heating rate of 15K / h.

[0190] The temperature, pressure, average particle size, particle size distribution and mesomorphous morphology evolution during the experiment are recorded and saved by the data acquisition system 12. The average particle size change and particle aggregation in the system during the hydrate slurry generation and decomposition process are shown in Table 2.

[0191] Comparative Example 1

[0192] After the stable hydrate slurry is formed in this comparative example, the experimental temperature is increased to 298.2K by direct heating, and no hydrate decomposition stabilizer is added during the decomposition process, and no staged heating is used.

[0193] In this comparative example, the hydrate reaction solution is an oil-water system (n-octane + water + hydrate inhibitor) containing 1% by weight of hydrate inhibitor and 10% by volume of water, the test gas is pure methane gas, and the hydrate inhibitor is a non-ionic surfactant composed of Span20 and Tween80 at a weight ratio of 1:1. The experimental temperature for hydrate slurry generation is 274.7K, and the experimental pressure is 5.8MPa.

[0194] The specific steps for hydrate slurry generation are as follows:

[0195] S1, 250mL of an oil-water system (n-octane + water + hydrate inhibitor) containing 1% by weight of hydrate inhibitor and 10% by volume of water is added to the high-pressure reaction kettle 2;

[0196] S2, set the temperature of the high-pressure reactor 2 to 274.7K, and introduce methane gas into the high-pressure reactor 2 through the gas cylinder 1 to 5.8MPa, as the temperature of the high-pressure reactor 2 decreases, hydrate particles begin to appear in the system, and after continuous reaction, stable hydrate slurry is obtained.

[0197] The specific steps of hydrate slurry decomposition are as follows:

[0198] (1) After the hydrate slurry is generated stably, the experimental temperature is directly increased to 298.2K at a rate of 15K / h.

[0199] The temperature, pressure, average particle size, particle size distribution and mesoscopic morphology evolution during the experiment are recorded and saved by the data acquisition system 12. The temperature / pressure changes during the generation and decomposition of the hydrate slurry of the oil-water system are shown in Figure 2 The change of the average particle size of the hydrate slurry of the oil-water system during the generation and decomposition process is shown in Figure 3 . Figure 4 The particle size distribution of the oil-water system at different stages is shown in Figures 5-9 The particle size mesoscopic morphology evolution of the oil-water system at different stages is shown in

[0200] As can be seen from Figure 2 , as the experimental temperature decreases and the methane gas is dissolved and absorbed in n-octane, when the experiment is performed to about 30min, the system pressure suddenly decreases twice, a large number of hydrate particles begin to appear, the system pressure continues to decrease and gradually balances at 4400kPa, then the temperature is directly increased to 25℃, the hydrate decomposition leads to gradual increase of the system pressure and finally tends to be stable (5600kPa).

[0201] Figure 3 The average particle size change curve is shown in the figure, and points A, B, C, D and E in the figure respectively represent the typical state before, during, after the generation of hydrate, after direct heating and during coalescence. As can be seen from Figure 2Before hydrate formation, the oil-water system, under the action of the hydrate inhibitor, was in an emulsion state with an average particle size of approximately 14.5 μm. Hydrate particles began to appear around 30 minutes into the experiment (point B), with slight fluctuations in the average particle size before gradually stabilizing at approximately 16.5 μm. After hydrate formation stabilized, the system became a slurry, demonstrating the effective inhibition of the hydrate inhibitor, preventing aggregation and clogging. Subsequently, when the temperature was directly and rapidly increased to 298.2 K, the average particle size of the system fluctuated dramatically to 26.2 μm (point D), with significant particle aggregation occurring. This fluctuation lasted for as long as 15 minutes. This secondary aggregation of particles during hydrate decomposition is caused by the rapid increase in experimental temperature during direct heating, which rapidly decomposed the hydrate particles to produce bubbles and water phase. Under the severe disturbance, the system aggregated, resulting in a dramatic increase in the average particle size, which increased the risk of reoccurrence of hydrate slurry clogging. Therefore, in practical applications, when decomposing hydrate slurries using a direct and rapid heating method, aggregation and clogging due to uncontrollable hydrate decomposition is highly likely to occur.

[0202] Figure 4 、 Figures 5-9 The particle size distribution and mesoscopic morphology evolution of different stages in a 10% volume oil-water system are respectively. Figure 4 and Figures 5-9 It can be seen that before hydrate formation, under the action of hydrate inhibitor and mechanical stirring, the oil-water system is in the form of a uniform emulsion ( Figure 5 ), there are a large number of particles distributed around the particle size of 10 μm, with the maximum number reaching 100; when the experimental temperature and pressure in the system reach the hydrate formation conditions, the droplets begin to gradually transform into hydrate particles and aggregate ( Figure 6 ), the corresponding number of particles dropped to about 40; with the continuous formation of hydrates, since the hydrate inhibitor can effectively prevent the accumulation between particles, with the continuous formation of hydrates, there is no large amount of accumulation between particles in the system, the average particle size and particle size distribution are relatively mild, and the final system is stable in the form of hydrate slurry ( Figure 7 ), uniform hydrate solid particles can be observed; when the experimental temperature is adjusted to 298.2K, Figure 8 and Figure 9 The secondary accumulation of hydrate particles can be clearly observed. Figure 4 The particle size distribution in the middle stage D shows that the number of particles in the observable size range drops sharply to about 10.

[0203] Comparative Example 2

[0204] The method of Comparative Example 1 was followed, except that the hydrate reaction liquid was an oil-water system (n-octane+water+hydrate inhibitor) containing 1 wt% hydrate inhibitor and 5% water by volume.

[0205] The average particle size of the hydrate slurry after stabilization, whether it is aggregated, and other specific conditions are shown in Table 2.

[0206] Comparative Example 3

[0207] In this comparative example, only the method of adding hydrate decomposition stabilizer was used to test whether aggregation would occur during the decomposition of the hydrate slurry, and the method of staged temperature increase was not used.

[0208] In this comparative example, the hydrate reaction liquid is an oil-water system (n-octane + water + hydrate inhibitor) containing 1% by weight of a hydrate inhibitor and a water content of 10% by volume. The experimental test gas is pure methane gas, and the hydrate inhibitor is a nonionic surfactant composed of Span20 and Tween80 in a weight ratio of 1:1. The experimental temperature for hydrate slurry generation is 274.7K and the experimental pressure is 5.8MPa. In the step (1), the hydrate decomposition stabilizer is composed of dodecyl glucoside and sodium alginate in a weight ratio of 1:1, and the amount of hydrate decomposition stabilizer added is 0.5% by weight of the water content in the hydrate reaction liquid.

[0209] The specific steps for generating hydrate slurry are:

[0210] S1, adding 250 mL of an oil-water system (n-octane + water + hydrate inhibitor) containing 1 wt% hydrate inhibitor and a water content of 10% by volume into autoclave 2;

[0211] S2. The temperature of the autoclave 2 is set to 274.7 K, and methane gas is introduced into the autoclave 2 through the gas cylinder 1 to a pressure of 5.8 MPa. As the temperature of the autoclave 2 decreases, hydrate particles begin to appear in the system. After continuous reaction, a stable hydrate slurry is obtained.

[0212] The specific steps of hydrate slurry decomposition are:

[0213] (1) After the hydrate slurry is generated and stabilized, the system pressure is 4438 kPa. The hydrate decomposition stabilizer is added to the hydrate slurry system under constant pressure through the injection pump 11, and the stirring is continued for 1.5 hours to ensure that the hydrate decomposition stabilizer is evenly dispersed in the entire system.

[0214] (2) Directly heat the sample to 298 K at a heating rate of 15 K / h.

[0215] The changes in the average particle size in the system and whether the particles coalesce during the formation and decomposition of the hydrate slurry are detailed in Table 2.

[0216] Comparative Example 4

[0217] The present comparative example only uses a staged heating method to test whether the hydrate slurry decomposition process will appear coalescence, without adding hydrate decomposition stabilizer.

[0218] In the present comparative example, the hydrate reaction solution is an oil-water system containing 1 wt% hydrate inhibitor, 10 vol% water (n-octane + water + hydrate inhibitor), the test gas is pure methane gas, and the hydrate inhibitor is a non-ionic surfactant composed of Span20 and Tween80 in a weight ratio of 1:1. The experimental temperature for hydrate slurry generation is 274.7 K, and the experimental pressure is 5.8 MPa.

[0219] The specific steps for hydrate slurry generation are as follows:

[0220] S1, 250 mL of oil-water system containing 1 wt% hydrate inhibitor, 10 vol% water (n-octane + water + hydrate inhibitor) is added into high-pressure reaction kettle 2;

[0221] S2, set the temperature of high-pressure reaction kettle 2 to 274.7 K, and pass methane gas into high-pressure reaction kettle 2 through gas cylinder 1 to 5.8 MPa. As the temperature of high-pressure reaction kettle 2 decreases, hydrate particles begin to appear in the system, and after continuous reaction, stable hydrate slurry is obtained.

[0222] The specific steps for hydrate slurry decomposition are as follows:

[0223] (1) After the hydrate slurry is generated stably, the system pressure is 4380 kPa, and the hydrate formation temperature is calculated to be 278.7 K using the Chen-Guo hydrate phase equilibrium model;

[0224] (2) The experimental temperature is quickly raised to 1 K below the hydrate phase equilibrium temperature corresponding to the system pressure (i.e. 277.7 K) at a rate of 4 K / h, and after temperature stabilization for 1.5 h;

[0225] (3) The experimental temperature is slowly raised to 0.5 K above the hydrate phase equilibrium temperature corresponding to the system pressure (i.e. 279.2 K) at a rate of 0.8 K / h, and after temperature stabilization for 3 h;

[0226] (4) The experimental temperature is continued to be slowly raised by 2 K (i.e. 281.2 K) at a rate of 0.8 K / h, and after temperature stabilization for 4 h;

[0227] (5) The experimental temperature is continued to be slowly raised by 3.0 K (i.e. 284.2 K) at a rate of 1.5 K / h, and after temperature stabilization for 4 h, the hydrate decomposition is observed, and the hydrate decomposition is basically completed;

[0228] (6) Rapidly increase the temperature to above 298 K at a heating rate of 15 K / h to completely decompose the remaining hydrates.

[0229] The changes in the average particle size in the system and whether the particles coalesce during the formation and decomposition of the hydrate slurry are detailed in Table 2.

[0230] Table 1

[0231]

[0232] Table 2

[0233]

[0234]

[0235] As can be seen from Table 2, using the method of the present invention, the hydrate slurry does not aggregate during the decomposition process. The "no aggregation" mentioned herein means that the maximum average particle size of the hydrate slurry during the decomposition process is always ≤ the average particle size of the stable hydrate slurry.

[0236] The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, various simple variations of the technical solution of the present invention may be made, including combining the various technical features in any other appropriate manner. These simple variations and combinations should also be regarded as disclosed in the present invention and fall within the scope of protection of the present invention.

Claims

1. A method for inhibiting the aggregation of hydrate slurry during decomposition, characterized in that: The method comprises the following steps: (1) adding a hydrate decomposition stabilizer to a hydrate slurry system and stirring, wherein the hydrate decomposition stabilizer comprises an alkyl glycoside compound and an alginic acid compound, and the weight ratio of the alkyl glycoside compound to the alginic acid compound is 1:0.1-10; (2) The temperature is raised to 1-2 K below the hydrate phase equilibrium temperature corresponding to the system pressure to perform the first stage decomposition, and the first stage decomposition time is ≥1 hour; (3) The temperature is raised to 0.5-1K above the hydrate phase equilibrium temperature corresponding to the system pressure to carry out the second stage decomposition, and the second stage decomposition time is ≥2 hours; (4) The system temperature is further increased by 1.8-2.2 K to perform the third stage decomposition, and the third stage decomposition time is ≥3 hours; (5) The system temperature is further increased by 2.8-3.2 K to perform the fourth stage decomposition, and the fourth stage decomposition time is ≥3 hours; (6) Raise the system temperature to above 298K to completely decompose the hydrate; The hydrate phase equilibrium temperature is calculated using the Chen-Guo hydrate phase equilibrium model.

2. The method according to claim 1, characterized in that The alkyl glycoside compound is selected from one or more of glucoside, dodecyl glucoside, dodecyl maltoside, dodecyl glucopyranoside and octyl glucopyranoside.

3. The method according to claim 1, characterized in that The alginic acid compound is selected from one or more of alginic acid, sodium alginate, calcium alginate, magnesium alginate and methacrylated sodium alginate.

4. The method according to claim 1, wherein The weight ratio of the alkyl glycoside compound to the alginic acid compound is 1:0.2-5.

5. The method according to claim 4, characterized in that The weight ratio of the alkyl glycoside compound to the alginic acid compound is 1:0.2-2.

6. The method according to claim 1, characterized in that The hydrate slurry is generated by the reaction of an oil-water system and gas.

7. The method according to claim 6, characterized in that The conditions for generating the hydrate slurry include: a temperature of 273.2-283.2 K and a pressure of 0-10 MPa.

8. The method according to claim 6, characterized in that The oil-water system contains hydrate inhibitor, water and n-octane.

9. The method according to claim 6, characterized in that The water content in the oil-water system is ≤20% by volume.

10. The method according to claim 8, characterized in that The content of the hydrate inhibitor in the oil-water system is 0.8-1.5 wt %.

11. The method according to claim 8, characterized in that The polymerization inhibitor is a surfactant.

12. The method according to claim 11, characterized in that The polymerization inhibitor is a nonionic surfactant.

13. The method according to claim 8, characterized in that The amount of the hydrate decomposition stabilizer used is 0.05-1% by weight of the amount of water in the oil-water system.

14. The method according to claim 13, wherein: The amount of the hydrate decomposition stabilizer used is 0.3-0.8 weight % of the amount of water in the oil-water system.

15. The method according to claim 1, wherein In step (1), the stirring time is ≥ 1 hour.

16. The method according to claim 15, characterized in that In step (1), the stirring time is 1.5 to 3 hours.

17. The method according to claim 1, wherein The system pressure in step (2) and step (3) is 4300~4600kPa.

18. The method according to claim 1, wherein In step (2), the heating rate is 3-5 K / h.

19. The method according to claim 1, wherein In step (2), the first stage decomposition time is 1.5 to 2 hours.

20. The method according to claim 1, wherein In step (3), the heating rate is 0.5~1K / h.

21. The method according to claim 1, wherein In step (3), the second stage decomposition time is 2.5 to 4 hours.

22. The method according to claim 1, wherein In step (4), the heating rate is 0.5~1K / h.

23. The method according to claim 1, wherein In step (4), the third stage decomposition time is 3.5 to 5 hours.

24. The method according to claim 1, wherein In step (5), the heating rate is 1~2K / h.

25. The method according to claim 1, wherein In step (5), the fourth stage decomposition time is 3.5 to 5 hours.

26. The method according to claim 1, wherein In step (6), the heating rate is 10-20 K / h.

27. The method according to claim 1, wherein The average particle size of the hydrate particles in the hydrate slurry is 10-20 μm.

28. The method according to claim 27, characterized in that The average particle size of the hydrate particles in the hydrate slurry is 15-17 μm.

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