Natural gas hydrate generation accelerant containing amino acid and nano calcium carbonate as well as preparation method and application of natural gas hydrate generation accelerant

Abstract

The invention discloses a natural gas hydrate generation accelerant containing amino acid and nano calcium carbonate as well as a preparation method and application of the natural gas hydrate generation accelerant, and belongs to the technical field of natural gas hydrates. The problems of low natural gas hydrate forming rate, low gas storage density, low natural gas recovery efficiency, poor environmental protection property and the like in the prior art are solved. The accelerant is obtained by taking a hydrophobic amino acid solution as a base solution, adding nano calcium carbonate into the base solution and adjusting or not adjusting the pH value. By regulating and controlling the type and the concentration of a base solution in the accelerant, the hydrate formation rate and the gas storage density are improved, and the induction time of hydrate generation is shortened; nanoparticles in the accelerant are small in particle size and large in specific surface area, so that disturbance and convective heat transfer of the accelerant are enhanced; in addition, the chemical components of the nanoparticles in the accelerant and the main component of the seabed sediment with a large amount of natural gas hydrate in the nature are calcium carbonate, the environmental risk is reduced, and the calcium carbonate and hydrophobic amino acid are wide in source and environmentally friendly.

Description

Technical Field

[0001] This invention belongs to the field of natural gas hydrate technology, specifically relating to a natural gas hydrate formation promoter containing amino acids and nano-calcium carbonate, its preparation method, and its application. Background Technology

[0002] Natural gas, as a clean energy source with abundant reserves and high calorific value, has attracted much attention amidst the continuous growth of global natural gas demand. The hydrate method for storing and transporting natural gas is considered a promising approach due to its numerous advantages. Natural gas hydrates are cage-like compounds formed by water and natural gas under suitable pH conditions and in a high-pressure, low-temperature environment. They can store large amounts of methane; theoretically, 1 cubic meter of methane can be stored. 3 Natural gas hydrates can be stored at approximately 170m³. 3 Standard-state natural gas offers significant economic advantages compared to compressed natural gas (CNG) and liquefied natural gas (LNG). However, this method has not yet achieved large-scale industrial application, primarily due to the slow formation kinetics of hydrates. To improve the formation rate of natural gas hydrates, existing technologies often employ mechanical enhancement methods, such as stirring, bubbling, and spraying, which can overcome the slow formation kinetics of natural gas hydrates to some extent. However, mechanical methods suffer from problems such as complex equipment, high energy consumption, and poor economic efficiency, and their effect on improving the formation rate of natural gas hydrates remains insufficient. The use of surfactants is considered an effective way to promote the formation rate of natural gas hydrates, with sodium dodecyl sulfate (SDS) being one of the effective kinetic promoters. However, synthetic chemical surfactants often have a certain degree of toxicity, especially anionic surfactants like SDS, which have a strong promoting effect on natural gas hydrates and pose certain environmental hazards. Furthermore, during use, they can easily cause foaming during the decomposition of natural gas hydrates, affecting gas recovery and reducing natural gas transportation efficiency. Summary of the Invention

[0003] In order to overcome the problems of slow formation rate, low gas storage density, low natural gas recovery efficiency and poor environmental performance of current natural gas hydrates, this invention provides a natural gas hydrate formation promoter containing amino acids and nano-calcium carbonate, its preparation method and application.

[0004] The technical solution of the present invention is as follows: One objective of this invention is to provide a natural gas hydrate formation promoter containing amino acids and nano-calcium carbonate. The promoter is prepared by mixing nano-calcium carbonate with a base liquid under conditions where the pH of the mixed liquid is adjusted or not adjusted. The base liquid is prepared by dissolving amino acids in water. The amino acids are L-leucine, L-methionine, or L-phenylalanine.

[0005] Further specifying, the concentration of nano-calcium carbonate in the accelerator is 800-2200 ppm.

[0006] Further specified, the base solution concentration is 1000-5000 ppm.

[0007] Further specifying, when the amino acid is L-leucine, the base solution concentration is 1000-5000 ppm.

[0008] Further specifying, when the amino acid is L-methionine, the base solution concentration is 1000-5000 ppm.

[0009] Further specifying, when the amino acid is L-phenylalanine, the base solution concentration is 1000-5000 ppm.

[0010] Further specifying, the particle size of nano-calcium carbonate is 20-60 nm.

[0011] Furthermore, the reagent used to adjust the pH of the mixed liquid is either acetic acid solution or sodium hydroxide solution.

[0012] Further, the pH of the mixed liquid was adjusted to 3-11.

[0013] The second objective of this invention is to provide a method for preparing the above-mentioned accelerator. The method is as follows: dissolve amino acids in water to prepare an amino acid solution, i.e., a base solution; add nano-calcium carbonate to the base solution; disperse by ultrasonication; adjust the pH of the resulting liquid or not adjust the pH to obtain the accelerator.

[0014] A third objective of this invention is to provide a method for preparing natural gas hydrates using the aforementioned promoter, the method comprising the following steps: S1. Rinse the high-pressure reactor, dry it, and then inject the accelerator; S2. Set the temperature. When the temperature inside the high-pressure reactor drops to the set temperature, purge with nitrogen to remove all the air from the high-pressure reactor. S3. After the air is exhausted, methane is introduced. When the pressure in the high-pressure reactor reaches 5-8 MPa, the air intake is stopped, and the stirring promoter is added to start the hydrate formation reaction. The reaction is stopped after 600 minutes to obtain natural gas hydrate.

[0015] Further specifying, the number of rinses in S1 is 3-4 times.

[0016] Further specifying, the temperature in S2 is 0-2℃.

[0017] Further specified, the stirring speed in S3 is 400-600 r / min.

[0018] The beneficial effects of this invention are as follows: (1) The natural hydrate promoter of the present invention includes nano-calcium carbonate and amino acids, wherein the amino acids are L-leucine, L-methionine or L-phenylalanine. Through the synergistic effect of nano-calcium carbonate and specific types and concentrations of hydrophobic amino acids, the formation rate of natural gas hydrate, gas storage density, natural gas recovery efficiency and environmental friendliness of hydrate synthesis method are improved.

[0019] (2) The promoter of the present invention is a nanofluid with L-leucine, L-methionine or L-phenylalanine solution as base liquid and added with nano-calcium carbonate, obtained under conditions of pH adjustment or no adjustment. Compared with ordinary solid suspensions, the promoter of the present invention has higher thermal conductivity and enhanced heat transfer performance. The promoter of the present invention introduces nano-calcium carbonate with small particle size and large specific surface area, which increases the heat exchange area between nanoparticles and base liquid. At the same time, the Brownian motion of nano-calcium carbonate in the promoter effectively enhances the micro-disturbance and convective heat transfer of the system, solves the heat transfer bottleneck problem in the hydrate formation process, and accelerates the nucleation and growth rate of hydrates.

[0020] (3) The present invention selects nano-calcium carbonate as one of the promoter components, which has chemical stability and environmental friendliness. Natural gas hydrates in nature are mainly distributed in deep-sea sedimentary layers, and the main component is CaCO3. The chemical composition of the nanoparticles in the promoter is consistent with the main component of the seabed sediments in which natural gas hydrates are abundant in nature, thus reducing environmental risks.

[0021] (4) The promoter and the method for synthesizing natural gas hydrate using the promoter proposed in this invention can effectively improve the gas storage capacity of natural gas hydrate. Among different concentrations of amino acid solutions, the one with the best promoting effect on natural gas hydrate is 3000 ppm L-leucine, and the gas storage capacity of natural gas hydrate is 126.5V. g / V w And there is no induction time. Attached Figure Description

[0022] Figure 1 Gas storage density of natural gas hydrates prepared using the promoters of Examples 1-3; Figure 2 Gas storage density of natural gas hydrates prepared using the promoters in Examples 4-6; Figure 3 Gas storage density of natural gas hydrates prepared using the promoters of Examples 7-9; Figure 4 Gas storage density of natural gas hydrates prepared using the promoters of Examples 10-14; Figure 5 The gas absorption amount in the natural gas hydrate formation process of Examples 10-14; Figure 6The diagram shows the gas absorption rate during the natural gas hydrate formation process in Examples 11-12. Detailed Implementation

[0023] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the examples in the specification.

[0024] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0025] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in different places in this specification does not necessarily refer to the same embodiment, nor is it a single or selective embodiment that is mutually exclusive with other embodiments.

[0026] Unless otherwise specified, the experimental methods used in the following examples are conventional methods. Unless otherwise specified, the materials, reagents, methods, and instruments used are all conventional materials, reagents, methods, and instruments in the art, and can be obtained commercially by those skilled in the art.

[0027] The gas storage density data described below in the text outside the table are the values ​​before the parentheses in the table, such as the gas storage density of 106.6 (±0.3) V in the table. g / V w The following text states that it is 106.6V. g / V w However, this does not affect the evaluation of the promoting effect of the accelerator of the present invention.

[0028] Comparative Example 1 S1. Weigh 400 mL of ultrapure water as an accelerator; S2. Rinse the high-pressure reactor with ultrapure water 3-4 times. After the high-pressure reactor is dry, inject the accelerator. S3. Set the temperature. When the temperature inside the high-pressure reactor drops to the set temperature of 0℃, open the air inlet and purge with nitrogen gas repeatedly to remove all the air from the high-pressure reactor and prevent impurities from interfering with the results. S4. After the air is exhausted, methane is introduced. When the pressure in the high-pressure reactor reaches 6 MPa, the air intake is stopped, and the stirrer is turned on at a stirring speed of 400 r / min to stir the promoter, thus initiating the hydrate formation reaction. The changes in temperature and pressure inside the high-pressure reactor are recorded using a data acquisition system, with data collected every 30 seconds. When the pressure inside the reactor tends to stabilize or changes very little, it indicates that the natural gas hydrate formation reaction is nearing completion. At this point, data acquisition can be stopped, but the temperature of the reaction system should be kept constant until the preset reaction time is reached, at which point the experiment is terminated. The preset reaction time is specified as 600 min from the start of stirring in S4. The experiment is repeated three times to eliminate errors, and the average value is taken. In this embodiment, the induction time during hydrate formation is 130 min.

[0029] Example 1 S1. Dissolve L-leucine in 400 mL of ultrapure water to prepare an L-leucine solution with a concentration of 1000 ppm, i.e., the base solution. Add 60 nm nano-calcium carbonate to the base solution to obtain a mixed solution. Stir with a magnetic stirrer for 60 min, and then disperse by ultrasonic bath for 15 min to ensure the stability of the nanoparticles in the solution to obtain a nanofluid, i.e., the promoter. The concentration of nano-calcium carbonate in the promoter is 2200 ppm. S2. Rinse the high-pressure reactor with ultrapure water 3-4 times. After the high-pressure reactor is dry, inject the accelerator. S3. Set the temperature. When the temperature inside the high-pressure reactor drops to the set temperature of 0℃, open the air inlet of the high-pressure reactor and purge with nitrogen gas repeatedly to remove the air from the high-pressure reactor and prevent impurities from interfering with the results. S4. After the air is exhausted, methane is introduced. When the pressure in the high-pressure reactor reaches 6 MPa, the air intake is stopped, and the stirrer is turned on at a stirring speed of 400 r / min to stir the promoter, thus initiating the hydrate formation reaction. The data acquisition system records the temperature and pressure changes inside the high-pressure reactor, acquiring data every 30 seconds. When the pressure inside the reactor tends to stabilize or changes very little, it indicates that the natural gas hydrate formation reaction is nearing completion. At this point, data acquisition can be stopped, but the temperature of the reaction system should be kept constant until the preset reaction time is reached before ending the experiment. The preset reaction time is specified as 600 min from the start of stirring in S4. The experiment is repeated three times to eliminate errors, and the average value is taken. In this embodiment, the induction time during hydrate formation is 50 min.

[0030] Example 2 The difference between this embodiment and Example 1 is that the concentration of the base solution (i.e., L-leucine solution) is 3000 ppm, the pH of the promoter is tested and the result shows that the pH is 8.22, there is no induction time in the hydrate formation process of this embodiment, and the remaining process steps and parameter settings are the same as in Example 1.

[0031] Example 3 The difference between this embodiment and Example 1 is that the concentration of the base solution (i.e., L-leucine solution) is 5000ppm, there is no induction time in the hydrate formation process of this embodiment, and the remaining process steps and parameter settings are the same as in Example 1.

[0032] Example 4 The difference between this embodiment and Example 1 is that L-leucine is replaced with L-methionine, there is no induction time in the hydrate formation process of this embodiment, and the remaining process steps and parameter settings are the same as in Example 1.

[0033] Example 5 The difference between this embodiment and Example 2 is that L-leucine is replaced with L-methionine, there is no induction time in the hydrate formation process of this embodiment, and the remaining process steps and parameter settings are the same as in Example 2.

[0034] Example 6 The difference between this embodiment and Example 3 is that L-leucine is replaced with L-methionine, there is no induction time in the hydrate formation process of this embodiment, and the remaining process steps and parameter settings are the same as in Example 3.

[0035] The gas storage density of the natural gas hydrates prepared in Examples 1-6 was tested, and the results are shown in the figure. Figure 1 , Figure 2 And Table 1, Figure 1 , Figure 2 The test results are shown in Table 1 for Examples 1-3 and Examples 4-6, respectively. The specific test data are shown in Table 1.

[0036] from Figure 1 , Figure 2 As can be seen from the data in Table 1, regardless of whether L-leucine or L-methionine is used, a base solution concentration of 3000 ppm has the best promoting effect on natural gas hydrates, with a gas storage density of 126.5V. g / V w 124.9V g / V w The concentration with the weakest promoting effect was 1000 ppm, with a gas storage density of 106.6 V. g / V w 92.8V g / V w When the concentration of the base solution formed by L-leucine and L-methionine in Examples 1-6 is 5000 ppm, the gas storage density is 122.8 V. g / V wThis indicates that as the concentration of the base liquid formed by L-leucine and L-methionine increases, the gas storage capacity of natural gas hydrate also increases. However, when the base liquid concentration exceeds 3000 ppm, the promoting effect on hydrate does not change significantly, and the gas storage density decreases compared to the base liquid concentration of 3000 ppm. This is because L-leucine and L-methionine are both hydrophobic aliphatic amino acids, and CaCO3 particles are also hydrophobic. A large number of amino acid molecules adsorb onto the surface of CaCO3 particles, forming aggregates. The higher the base liquid concentration, the more amino acids there are, and the larger the aggregate volume. The strong hydrophobicity of amino acids and nano-calcium carbonate reduces the contact between the aggregates and H2O molecules, leading to agglomeration in the promoter and ultimately a small amount of precipitation. This reduces the dispersibility and stability of the nanofluid, affecting the gas-liquid mass transfer process, resulting in a less significant promoting effect on natural gas hydrate compared to the concentration of 3000 ppm. Although the best promoting effect is achieved at a base liquid concentration of 3000 ppm when the base liquid concentration is between 1000-5000 ppm, other base liquid concentrations within this range still have a good promoting effect on natural gas hydrate formation, and the gas storage density remains high.

[0037] Example 7 The difference between this embodiment and Example 1 is that L-leucine is replaced with L-phenylalanine, the induction time for hydrate formation in this embodiment is 30 min, and the remaining process steps and parameter settings are the same as in Example 1.

[0038] Example 8 The difference between this embodiment and Example 2 is that L-leucine is replaced with L-phenylalanine, the induction time for hydrate formation in this embodiment is 125 min, and the remaining process steps and parameter settings are the same as in Example 2.

[0039] Example 9 The difference between this embodiment and Example 3 is that L-leucine is replaced with L-phenylalanine, the induction time for hydrate formation in this embodiment is 40 min, and the remaining process steps and parameter settings are the same as in Example 3.

[0040] The gas storage density of the natural gas hydrates prepared in Examples 7-9 was tested, and the results are shown in the figure. Figure 3 See Table 1. It can be seen that when L-phenylalanine is used, the gas storage density of the hydrate in the accelerator prepared with base solutions of 1000, 3000, and 5000 ppm is 108.2 V, respectively. g / V w 127.5V g / V w and 129.7V g / V wWhen the base solution concentration was 3000 ppm or 5000 ppm, the gas storage density of natural gas hydrate was not significantly different regardless of whether L-phenylalanine, L-leucine, or L-methionine was used. However, in Examples 8 and 9, which used L-phenylalanine solutions with concentrations of 3000 ppm and 5000 ppm, induction times were observed, at 125 min and 40 min, respectively. This indicates that the promoting effect on natural gas hydrate formation is enhanced with increasing base solution concentration of phenylalanine. This is because phenylalanine is a hydrophobic aromatic amino acid, and aromatic amino acids all contain benzene ring structures in their side chains. Due to the combined effects of the benzene ring's conjugated system, the side chain connection mode, electroneutrality and chemical inertness, π-π stacking, and resonance stabilization, phenylalanine can exist stably and is not prone to reacting with other compounds. A relatively high concentration of phenylalanine is required for the promoting effect to become significant.

[0041] Example 10 The difference between this embodiment and embodiment 2 is that: acetic acid solution with a concentration of 3wt% is added to the nanofluid obtained in S2 to adjust the pH until the pH of the nanofluid is 3, thus obtaining a nanofluid with pH 3, which is the promoter. There is no induction time in the hydrate formation process of this embodiment, and the remaining process steps and parameter settings are the same as in embodiment 2.

[0042] Example 11 The difference between this embodiment and embodiment 2 is that: acetic acid solution with a concentration of 3wt% is added to the nanofluid obtained in S2 to adjust the pH until the pH of the nanofluid is 5, thus obtaining a nanofluid with pH 5, which is the promoter. The induction time in the hydrate formation process of this embodiment is 25 min, and the remaining process steps and parameter settings are the same as in embodiment 2.

[0043] Example 12 The difference between this embodiment and embodiment 2 is that: an acetic acid solution with a concentration of 3wt% is added to the nanofluid obtained in S2 to adjust the pH until the pH of the nanofluid is 7, thus obtaining a nanofluid with a pH of 7, which is the promoter. There is no induction time in the hydrate formation process of this embodiment, and the remaining process steps and parameter settings are the same as in embodiment 2.

[0044] Since the pH of the nanofluid (accelerator) in Example 2 was 8.22 without pH adjustment, an acidic substance should be added to adjust the pH to 7 in this example. Therefore, acetic acid solution is used for adjustment.

[0045] Example 13 The difference between this embodiment and embodiment 2 is that a 2wt% sodium hydroxide solution is added to the nanofluid obtained in S2 to adjust the pH until the pH of the nanofluid is 9, thus obtaining a nanofluid with pH 9, which is the promoter. The induction time during the hydrate formation process in this embodiment is 40 min, and the remaining process steps and parameter settings are the same as in embodiment 2.

[0046] Example 14 The difference between this embodiment and embodiment 2 is that sodium hydroxide with a concentration of 2wt% is added to the nanofluid obtained in S2 to adjust the pH of the solution until the pH of the nanofluid is 11, thus obtaining a nanofluid with a pH of 11, which is the promoter. The induction time in the hydrate formation process of this embodiment is 25 min, and the remaining process steps and parameter settings are the same as in embodiment 2.

[0047] The gas storage density of the natural gas hydrates prepared in Examples 10-14 was tested, and the results are shown in the figure. Figure 4 And Table 1. The gas absorption of natural gas hydrates prepared in Examples 10-14, i.e., with different pH promoters, was tested, and the results are shown in Table 1. Figure 5 And Table 1. From Figure 4 , 5 It can be seen that under strongly acidic conditions with pH=3, from Figure 5 It was observed that the gas absorption reached 0.005 mol / mol after 50 minutes, and subsequently reached 0.0097 mol / mol, a change of approximately 0.004 mol / mol. This suggests that the natural gas hydrate formation was complete within 50 minutes. Therefore, it can be concluded that under pH=3 conditions, hydrate formation ended within a short time, with a gas absorption of 0.0097 mol / mol. This is because CaCO3 particles react with acetic acid to form calcium acetate, resulting in a lack of nucleation sites for hydrate in the promoter. This hinders the mass transfer process between the gas and liquid phases, reduces the gas-liquid contact area, and thus inhibits the large-scale formation of hydrate. Furthermore, calcium acetate often exists in the form of hydrated Ca(CH3COO)2·H2O, which is generally more stable. Under strongly alkaline conditions at pH=11, the gas storage density and gas absorption of natural gas hydrate were 59.6 V. g / V w The reaction was completed at 0.0302 mol / mol for 100 min, with an induction time of 25 min. Although NaOH solution cannot react with CaCO3 particles, and there are many hydrate nucleation sites in the nanofluid, NaOH is a strong electrolyte and completely ionizes into Na+ in the liquid phase. + and OH -These ions undergo strong hydration with H2O molecules, consuming a large number of free H2O molecules and competing for them. The formation of the cage-like structure of the hydrate requires a large number of relatively free, directionally aligned H2O molecules, significantly reducing the water activity available for constructing the hydrate crystal structure and consequently lowering the chemical potential of water. This increases the pressure required for hydrate formation or lowers the temperature. This means that under the same pressure and temperature, the addition of NaOH makes it less likely for natural gas hydrates to form, or the conditions for hydrate formation become more demanding, resulting in a longer induction time. This result is also confirmed in Example 13 at pH 9, where the induction time in Example 9 was 40 min; under weakly acidic conditions with a promoter pH of 5, the gas storage capacity of the natural gas hydrate was 128.6 V. g / V w The gas storage density was 124.4 V under neutral conditions (pH 7) in Example 12. g / V w The difference is not significant, but as Figure 6 As shown, the gas absorption rate of natural gas hydrate was the highest in the first 100 minutes, at 0.000325 mol / mol / min, which can be considered the induction period. In summary, the promoters at pH 3-11 all had a promoting effect on natural gas hydrates. However, at pH 7, the promoter with 3000 ppm leucine as the base solution showed the best promoting effect. The reason for this is that under neutral conditions, the protonation state of the carboxyl and amino groups of leucine reaches an equilibrium point, making the entire leucine molecule electrically neutral with zero net charge. Without additional net charge attracting water molecules, the hydrophobic groups can most effectively repel water molecules, resulting in the strongest hydrophobicity. This strong hydrophobicity makes leucine molecules more inclined to aggregate at the gas-liquid and solid-liquid interfaces, reducing interfacial tension and decreasing the work done on hydrate nucleation. Moreover, under acidic or alkaline conditions, the charge on leucine molecules may cause them to aggregate, reducing the effectiveness of the amino acid and hindering adsorption of CaCO3 nanoparticles. Therefore, the promoting effect of the promoter is worse than under neutral conditions.

[0048] Table 1 Performance test results of natural gas hydrates in Examples 1-14

[0049] Note: T 90 It is the time required from the start of the reaction until the system reaches 90% of its final total gas consumption.

[0050] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A natural gas hydrate formation accelerator comprising an amino acid and nano-sized calcium carbonate, characterized by, The accelerator is prepared by mixing nano calcium carbonate with a base solution under the condition of adjusting the pH of the mixed solution or without adjusting the pH of the mixed solution; The base solution is prepared by dissolving amino acid in water.

2. The accelerator according to claim 1, characterized in that, The amino acid is L-leucine, L-methionine or L-phenylalanine.

3. The accelerator according to claim 1, characterized in that, The concentration of nano calcium carbonate in the accelerator is 800-2200 ppm.

4. The accelerator according to claim 1, characterized in that, The particle size of nano calcium carbonate is 20-60 nm.

5. The accelerator according to claim 1, characterized in that, The reagent for adjusting the pH of the mixed solution is acetic acid solution or sodium hydroxide solution.

6. The accelerator according to claim 1, characterized in that, The pH of the mixed solution is adjusted to 3-11.

7. A process for the preparation of the accelerator as claimed in any one of claims 1 to 6, characterized in that, The preparation method comprises the following steps:

8. A method for producing natural gas hydrate using the promoter according to any one of claims 1 to 6, characterized by, S1, flushing the high-pressure reactor and drying it before injecting the accelerator; S2, setting the temperature, and when the temperature in the high-pressure reactor reaches the set temperature, purging with nitrogen to exhaust the air in the high-pressure reactor; S3, after the air is exhausted, methane is filled in, and when the pressure in the high-pressure reactor reaches 5-8 MPa, the gas inlet is stopped, the accelerator is stirred, and the hydrate formation reaction is started, and the reaction is stopped after 600 min to obtain natural gas hydrate. The temperature in S2 is 0-2℃.

9. The production method according to claim 8, characterized by, The stirring speed in S3 is 400-600 r / min.

10. The preparation method according to claim 8, characterized in that, ​

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