CN113817443B - Hydrate decomposition inhibiting composition, coupling enhanced solid hydrate and method for enhancing storage and transportation stability of solid hydrate - Google Patents
Hydrate decomposition inhibiting composition, coupling enhanced solid hydrate and method for enhancing storage and transportation stability of solid hydrate Download PDFInfo
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Abstract
The invention relates to the technical field of safe storage and transportation of natural gas, and discloses a hydrate decomposition inhibiting composition, a coupling enhanced solid hydrate and a method for enhancing the storage and transportation stability of the solid hydrate, wherein the hydrate decomposition inhibiting composition contains a starch-based surfactant, wherein the starch-based surfactant comprises sodium carboxymethyl starch and alkyl glycoside surfactant, which not only can be used as surfactant to improve the interface stability of hydrate phase boundary, and the colloidal solution formed by dispersing the sodium carboxymethyl starch and the alkyl glycoside surfactant in water can coat the surface of the hydrate to form a protective layer, thus, the mechanical stability of the hydrate can be improved, the strength of the crystal interface of the hydrate is enhanced, therefore, the structural stability of the hydrate is improved, the decomposition of the hydrate is inhibited, the decomposition rate of the hydrate is reduced, and the decomposition amount of the hydrate can be further reduced.
Description
Technical Field
The invention relates to the technical field of natural gas safe storage and transportation, in particular to a hydrate decomposition inhibiting composition, a coupling enhanced solid hydrate and a method for enhancing the storage and transportation stability of the solid hydrate.
Background
The solid hydrate natural gas storage and transportation technology has many advantages, such as relatively high gas storage capacity; the storage process with non-explosive characteristic, relative safety and reliability and the like are used as a new substitute gas storage technology and are widely researched and applied in the industry. However, in the storage and transportation stage of the solid hydrate, the existing storage and transportation technology mostly utilizes the self-protection effect of the hydrate to store at low temperature, but in the storage and transportation process of the hydrate in the prior art, the hydrate is unstable in structure, so that the decomposition rate of the hydrate is higher. In this case, two measures are generally taken: a part of stored natural gas is released to ensure normal-pressure storage and transportation, but the waste of the natural gas is caused; or, the pressure-resistant storage and transportation device is adopted for storage and transportation, so that the requirements on the storage and transportation equipment are improved, and the storage and transportation cost is increased.
The patent application CN201910777510.2 Chenjun in the invention of a method for inhibiting hydrate decomposition and a hydrate storage and transportation method discloses a method for inhibiting hydrate decomposition and a hydrate storage and transportation method, comprising the following steps: after the hydrate is formed, covering the surface of the hydrate with a hydrate promoter, wherein the hydrate promoter comprises at least one of tetrahydrofuran or cyclohexane, and covering the surface of the hydrate with a substance with a lower melting point, wherein the lower melting point is (0-20) DEG C, and the substance with the lower melting point comprises n-tetradecane, so that the later decomposition of the hydrate is inhibited. Proved by verification, after 12-13 hours of decomposition, the final hydrate decomposition percentage is controlled to be 12.4-23.9%. It can be seen that the method has a limited effect on inhibiting the rate of hydrate decomposition.
The Chinese patent application CN201811304730.5 discloses a hydrate decomposition inhibitor suitable for drilling a natural gas hydrate stratum, which comprises the following raw materials in percentage by mass: 0-100% of poly 3-methylene 2-pyrrolidone, 0-100% of lecithin and 0-100% of poly N-vinyl pyrrolidone. The method inhibits the decomposition of the hydrate by filling the hydrate decomposition inhibitor, and verifies the effect of the drilling fluid on inhibiting the decomposition of the hydrate by the time required for the complete decomposition of the hydrate, and finds that the complete decomposition of the hydrate needs 8 hours without adding the hydrate decomposition inhibitor, and the complete decomposition of the hydrate needs 10.4 to 18.4 hours after filling the hydrate decomposition inhibitor. While the conventional hydrate storage and transportation is generally higher than 18 hours, the method has a limited effect on inhibiting the decomposition of the hydrate.
Therefore, how to further reduce the decomposition rate of the hydrate and further reduce the decomposition amount of the hydrate while ensuring that the solid hydrate has the advantage of higher gas storage capacity so as to meet the conventional storage and transportation requirements is a technical problem to be solved at present.
Disclosure of Invention
The invention aims to overcome the technical problem of poor solid hydrate decomposition inhibiting effect in the prior art, and provides a hydrate decomposition inhibiting composition, a coupling enhanced solid hydrate and a method for enhancing the storage and transportation stability of the solid hydrate, which can effectively reduce the hydrate decomposition rate and reduce the decomposition amount of the hydrate, thereby reducing the waste of gas in the storage and transportation process and reducing the pressure-bearing requirement on storage and transportation equipment.
In order to achieve the above objects, according to one aspect of the present invention, there is provided a hydrate decomposition inhibiting composition comprising a starch-based surfactant, wherein the starch-based surfactant comprises sodium carboxymethyl starch and an alkyl glycoside-type surfactant.
The invention provides a coupling enhanced solid hydrate, which comprises a solid hydrate core and a hydrate protective layer coating the solid hydrate core; wherein the hydrate protective layer contains sodium carboxymethyl starch and alkyl glycoside surfactant.
In yet another aspect, the invention provides a method for enhancing the storage and transportation stability of solid hydrates, comprising: after the solid hydrate core is formed, adding a dispersion liquid containing a starch-based surfactant to a system containing the solid hydrate core under the solid hydrate generating conditions to form a hydrate protective layer coating the solid hydrate core outside the solid hydrate core; wherein the starch-based surfactant comprises sodium carboxymethyl starch and alkyl glycoside surfactant.
In the above technical solution, the sodium carboxymethyl starch and the alkyl glycoside surfactant contained in the hydrate decomposition inhibiting composition of the present invention not only serve as surfactants to improve the interface stability of the phase boundary of the hydrate, but also form a protective layer by coating the surface of the hydrate with a colloidal solution formed by dispersing the sodium carboxymethyl starch and the alkyl glycoside surfactant in water, so as to improve the mechanical stability of the hydrate, enhance the strength of the crystal interface of the hydrate, and improve the structural stability of the hydrate, thereby inhibiting the decomposition of the hydrate, reducing the decomposition rate of the hydrate, and further reducing the decomposition amount of the hydrate.
It was confirmed, for example, that in example 7, after the formation of the hydrate core was completed, the hydrate decomposition inhibiting composition containing the starch-based surfactant of the present invention was injected to form a hydrate protective layer on the surface of the solid hydrate core, and after the hydrate protective layer was completely formed, a coupling-enhanced solid hydrate containing the hydrate protective layer was obtained. And then recording the pressure change in the reaction kettle within 18h of continuous decomposition in real time under the atmospheric pressure, and calculating the decomposition release amount of the hydrate to be 12.49mmol and the decomposition rate of the hydrate to be 13.58% according to the pressure change from the atmospheric pressure to the final pressure in the reaction kettle. In the case where the hydrate protective layer of the present invention was not included, for example, in comparative example 1, after the solid hydrate was formed, the change in the pressure in the reaction vessel within 18 hours of continuous decomposition was recorded in real time under atmospheric pressure, and the amount of released hydrate decomposed was calculated as 25mmol from the change from atmospheric pressure to the last pressure in the reaction vessel, and the decomposition rate of the hydrate was 27.17%.
Drawings
FIG. 1 is a schematic diagram of a coupled enhanced solid hydrate according to an embodiment of the present invention.
Description of the reference numerals
1 hydrate crystal 2 hydrate shell
3 hydrate protective layer 4 adsorption-absorption protective layer
5 layer of ice
Detailed Description
The endpoints of the ranges and any values disclosed herein are not limited to the precise range or value, and such ranges or values should be understood to encompass values close to those ranges or values. For ranges of values, between the endpoints of each of the ranges and the individual points, and between the individual points may be combined with each other to give one or more new ranges of values, and these ranges of values should be considered as specifically disclosed herein.
In one aspect, the present invention provides a hydrate decomposition inhibiting composition comprising a starch-based surfactant, wherein the starch-based surfactant comprises sodium carboxymethyl starch and an alkyl glycoside surfactant.
In order to further improve the interface stability of a hydrate phase boundary and improve the structural stability of the hydrate, thereby inhibiting the decomposition of the hydrate and reducing the decomposition rate of the hydrate, the mass ratio of the sodium carboxymethyl starch to the alkyl glycoside surfactant is 1: 1-3; preferably 1: 1.5-2.5.
The alkyl glycoside surfactant is a product of saccharide compound and fatty alcohol, and its molecular structure can be represented by RO (G) n Is represented by the formula (shown below), wherein R represents an alkyl group, generally C 8 -C 18 Saturated straight or branched chain alkyl; g represents a saccharide unit; n represents the number of sugar units, and is called alkyl monoglycoside when n is 1, Alkyl Polyglycoside (APG) when n is more than or equal to 2, and preferably n is a positive integer of 1 to 3.
Preferably, the alkyl glycoside surfactant is at least one of APG0810, APG0814, APG1214, APG0816, and APG 1216.
Sodium carboxymethyl starch is available in various commercial products, the sodium content may be 2-7 wt%, the degree of substitution D.S may be 0.3-0.6, the viscosity of 2 wt% aqueous solution (25 ℃) may be 300-1200mpa.s, and the pH of 1 wt% aqueous solution may be in the range of 6.5-11.5.
In order to further reduce the pressure-bearing requirements of storage and transportation equipment due to hydrate decomposition, or gas waste caused thereby, the hydrate decomposition inhibiting composition further comprises an adsorption-absorption agent stored separately from the starch-based surfactant; wherein the adsorption-absorption agent is a liquid with higher solubility for the gas in the hydrate or a solid capable of absorbing the gas in the hydrate. Thus, even if the hydrate is decomposed, the released gas can be absorbed by the adsorption-absorption agent, so that the pressurization amplitude in the system caused by the decomposition of the hydrate is reduced, and the storage and transportation safety can be maintained without releasing the gas; higher pressure-bearing equipment is not needed, and the pressure-bearing requirement on storage and transportation equipment is reduced.
Preferred adsorption-absorbents include porous adsorbent materials and multi-carbon linear alkanes. The multi-carbon straight-chain alkane has higher solubility to gas in natural gas such as methane, and the porous adsorption material has higher adsorption capacity, and is favorable for dispersion and convenient for absorption and capture of released gas. Moreover, the adsorption-absorption agent not only has better dissolving and absorbing performance to gas, especially natural gas, but also can be matched with a protective layer formed by sodium carboxymethyl starch and alkyl glycoside surfactants so as to be attached and covered on the protective layer containing the sodium carboxymethyl starch and the alkyl glycoside surfactants. The sodium starch glycolate and the alkyl glycoside surfactant can also serve as a binding agent. Preferably, the mass ratio of the starch-based surfactant to the adsorption-absorption agent is 0.5-10: 1.
Preferably, the mass ratio of the porous adsorption material to the multi-carbon straight-chain alkane is 0.5-10:100, preferably 1-5: 100.
as described above, the present invention can be implemented as long as the porous adsorbent has a good adsorption performance to gas, and preferably, the porous adsorbent is a nano-scale material, that is, porous fine particles having a particle size of 1 to 100 nm. Further preferably, the porous adsorption material is at least one of expanded graphite, nano graphite, carbon nanotubes, graphene, an ordered mesoporous molecular sieve and a metal organic framework material. Similarly, organic liquids having a relatively high solubility for gases in natural gas such as methane can be used to practice the present invention, preferably, the multi-carbon linear alkane is a linear alkane having 5 to 15 carbon atoms; further, the multi-carbon linear alkane is at least one of n-hexane, n-heptane, n-octane, n-nonane, n-decane and n-undecane.
The invention provides a coupling enhanced solid hydrate, which comprises a solid hydrate core and a hydrate protective layer coating the solid hydrate core; wherein the hydrate protective layer contains sodium carboxymethyl starch and alkyl glycoside surfactant.
Therefore, the hydrate protective layer containing the sodium carboxymethyl starch and the alkyl glycoside surfactant improves the interface stability of a hydrate phase boundary, improves the mechanical stability of the hydrate, enhances the strength of a hydrate crystal interface, improves the structural stability of the hydrate, inhibits the decomposition of the hydrate, reduces the decomposition rate of the hydrate, and further can reduce the decomposition amount of the hydrate.
Preferably, the mass ratio of the sodium carboxymethyl starch to the alkyl glycoside surfactant is 1: 1.5-2.5.
Preferably, the coupling enhanced solid hydrate further comprises an adsorption-absorption protective layer coated outside the hydrate protective layer; the adsorption-absorption protective layer contains an adsorption-absorption agent. Thus, even if the hydrate is decomposed, the released gas can be absorbed by the adsorption-absorption agent, so that the pressurization amplitude in the system caused by the decomposition of the hydrate is reduced, and the storage and transportation safety can be maintained without releasing the gas; higher pressure-bearing equipment is not needed, and the pressure-bearing requirement on storage and transportation equipment is lowered. Preferably, the adsorption-absorption agent contains a porous adsorption material and a multi-carbon linear alkane. Preferably, the mass ratio of the porous adsorption material to the multi-carbon straight-chain alkane is 0.5-10: 100; preferably 1 to 5: 100. in order to further reduce the gas diffusion mass transfer rate after the hydrate is decomposed and improve the stability of the hydrate structure. Preferably, the coupling-enhanced solid hydrate further comprises an ice layer coated outside the adsorption-absorption protective layer.
In a preferred embodiment of the present invention, as shown in fig. 1, the coupling enhanced solid hydrate comprises a solid hydrate core, and a hydrate protective layer 3, an adsorption-absorption protective layer 4 and an ice layer 5 which are sequentially coated on the outer side of the solid hydrate core from inside to outside by taking the solid hydrate core as a core. Compared with the prior art, the method comprises the steps of providing a solid hydrate core body with a self-protection effect at low temperature, adding a hydrate protective layer 3, an adsorption-absorption protective layer 4 and an ice layer 5 on the basis, and covering the hydrate protective layer 3 containing the hydrate decomposition inhibiting composition, the adsorption-absorption protective layer 4, the artificially thickened ice layer 5 and the like on the surface of the solid hydrate core body through multi-level coupling. The method can reduce the pressure requirement of the hydrate gas storage process, thereby further improving the stability and safety of the gas storage process.
The solid hydrate core body is shown in figure 1 and comprises a hydrate shell layer 2 and a plurality of hydrate crystals 1 coated in the hydrate shell layer 2. The hydrate shell layer 2 can be a conventional ice layer, or a solid shell layer formed by a porous material or a phase-change material, and the technical effect of the invention is not influenced by the change of the structure of the solid hydrate core body.
In another aspect, the present invention provides a method for enhancing storage and transportation stability of solid hydrate, comprising: after the solid hydrate core is formed, adding a dispersion liquid containing a starch-based surfactant to a system containing the solid hydrate core under the solid hydrate generating conditions to form a hydrate protective layer coating the solid hydrate core outside the solid hydrate core; wherein the starch-based surfactant comprises sodium carboxymethyl starch and alkyl glycoside surfactant. As described above, the sodium carboxymethyl starch and the alkyl glycoside surfactant not only serve as surfactants to improve the interface stability of the phase boundary of the hydrate, but also can coat the surface of the hydrate with a colloidal solution formed by dispersing the sodium carboxymethyl starch and the alkyl glycoside surfactant in water to form a protective layer, so that the mechanical stability of the hydrate can be improved, the strength of the crystal interface of the hydrate is enhanced, the structural stability of the hydrate is improved, the decomposition of the hydrate is inhibited, the decomposition rate of the hydrate is reduced, and the decomposition amount of the hydrate can be further reduced.
Preferably, the mass ratio of the sodium carboxymethyl starch to the alkyl glycoside surfactant is 1:1-3, preferably 1: 1.5-2.5.
In order to facilitate the decomposition of the solid hydrate before use after the gas is stored and transported to a site on the basis of inhibiting the decomposition of the hydrate, the mass ratio of the starch-based surfactant to the dispersion is preferably 0.5-10:100, preferably 1-5: 100, respectively; it is further preferred that the volume ratio of the dispersion containing the starch-based surfactant to the initial aqueous system forming the solid hydrate nuclei is not more than 15:100, it is further preferred that the volume ratio is from 6 to 12: 100.
preferably, the method for enhancing the storage and transportation stability of the solid hydrate further comprises the steps of adding an adsorption-absorption agent into the system after the hydrate protective layer is formed and under the conditions that the solid hydrate is in a self-protection effect temperature range and the pressure of the system is close to and higher than the phase equilibrium pressure of the hydrate in the temperature range so as to form an adsorption-absorption protective layer coating the hydrate protective layer outside the hydrate protective layer; thus, even if the hydrate is decomposed, the released gas can be stored by the adsorption-absorption agent, so that the pressurization amplitude in the system caused by the decomposition of the hydrate is reduced, and the storage and transportation safety can be maintained without releasing the gas; higher pressure-bearing equipment is not needed, and the pressure-bearing requirement on storage and transportation equipment is reduced. Preferably, the adsorption-absorption agent comprises a porous adsorption material and a multi-carbon straight-chain alkane; further preferably, the mass ratio of the porous adsorption material to the multi-carbon linear alkane is 0.5-10:100, preferably 1-5: 100, respectively; preferably, the self-protection effect temperature range of the solid hydrate is 253.15K-272.15K; preferably, the hydrate phase equilibrium pressure over the self-protective effect temperature range is equal to the pressure calculated by the Chen-Guo hydrate phase equilibrium equation.
To facilitate decomposition of solid hydrates after storage and transportation to site, prior to use, while inhibiting hydrate decomposition, it is preferred that the volume ratio of adsorbent-absorbent to initial aqueous system forming the solid hydrate nuclei does not exceed 15: 100; the volume ratio is preferably (5-10): 100.
preferably, the method for enhancing the storage and transportation stability of the solid hydrate further comprises adding water into the system after the adsorption-absorption protective layer is formed and when the temperature of the system is below the freezing point, so as to form an ice layer coating the adsorption-absorption protective layer outside the adsorption-absorption protective layer. Thereby further reducing the diffusion mass transfer rate of the gas after the hydrate is decomposed and improving the structural stability of the hydrate.
Preferably, the volume ratio of water added to form the ice layer to the initial aqueous system forming the solid hydrate nuclei does not exceed 5: 100; further preferred is a volume ratio of 2 to 4: 100.
wherein the solid hydrate nuclei can be obtained by any solid hydrate forming means known in the art, for example, the solid hydrate nuclei can be obtained by: a gas is contacted with a hydrate promoter in an aqueous system containing the hydrate promoter under solid hydrate forming conditions. Preferably, the solid hydrate forming conditions include: the temperature is 273.15-293.15K, preferably 273.15-283.15K; the pressure range is 0.5-20 MPa; the hydrate accelerating agent is a thermodynamic hydrate accelerating agent and/or a kinetic hydrate accelerating agent.
In order to improve the stability of the hydrate and reduce the decomposition of the hydrate, the hydrate accelerating agent preferably consists of a thermodynamic hydrate accelerating agent and a kinetic hydrate accelerating agent; further preferably, the mass ratio of the thermodynamic hydrate accelerant to the kinetic hydrate accelerant is 1: 0.1-10.
The thermodynamic hydrate accelerant can adopt the conventional thermodynamic hydrate accelerant in the field such as tetrahydrofuran, cyclopentane, tetrabutylammonium bromide, tetrabutylammonium chloride, tetrabutylammonium fluoride, tetrabutylammonium phosphate, tert-butyl peroxybenzoate and the like; in order to improve the stability of the hydrate, preferably, the thermodynamic hydrate promoter is at least one of tetrahydrofuran, cyclopentane, tetrabutylammonium bromide and tetrabutylammonium chloride.
In order to improve the stability of the hydrate and reduce the decomposition of the hydrate, the kinetic hydrate accelerant is preferably an amino acid hydrate accelerant, and more preferably at least one of leucine, arginine, histidine, glutamic acid and phenylalanine.
Preferably, the mass ratio of the hydrate accelerant to water in the aqueous system is 0.1-5: 100.
preferably, the hydrate formation temperature is 273.15-293.15K, more preferably 273.15-283.15K.
Preferably, the hydrate formation pressure is in the range of 0.5 to 20 MPa;
in the foregoing, the volume of the initial aqueous system of solid hydrate nuclei refers to the volume of the aqueous phase containing the hydrate promoter prior to formation of the conventional solid hydrate.
In the present invention, unless otherwise specified, the pressure therein refers to gauge pressure.
While for the water to gas ratio, proportions conventional in the art may be used, it is preferred that during hydrate formation, an excess of charge gas be ensured in relation to 1 cubic meter of water stored up to 185 cubic meters.
In the above technical solution, the gas may be a single gas requiring storage and transportation, such as methane, ethane, propane, carbon dioxide, hydrogen, or a mixture of gases, such as natural gas, associated gas in an oil production process, and associated gas in a natural gas production process. The invention also has good application prospect in the aspects of storage and transportation of acid gas, oil-gas associated gas and the like.
The type of the reactor in the present invention is not particularly limited, and may be, for example, a high-pressure reactor, and the present invention can be realized as long as the conditions for producing the hydrate in the present invention can be satisfied.
In a particular embodiment of the invention, the solid hydrate nucleus is obtained by:
(1) adding a hydrate accelerant into a reaction kettle with water, setting reaction temperature and reaction pressure, keeping the temperature and the pressure constant in the hydrate generation process, introducing gas into the reactor, and contacting the gas with the hydrate accelerant in a water-containing system.
And calculating the actual generation amount of the hydrate in the system by adopting a hydrate thermodynamic equilibrium equation according to the gas volume consumed by the reaction system, the reaction temperature and the reaction pressure.
In a specific embodiment of the invention, the method for enhancing the storage and transportation stability of the solid hydrate comprises the following steps:
(1) preparation of solid hydrate nuclei: adding a hydrate accelerant into a reaction kettle with water, setting the reaction temperature and the reaction pressure of hydrate generation conditions, introducing gas into the reactor, and contacting the gas with the hydrate accelerant in a water-containing system;
(2) after the solid hydrate core body is formed in the step (1), adding a certain volume of dispersion liquid containing starch-based surfactant into a high-pressure reaction system, and forming a hydrate protective layer on the surface of the initial solid hydrate core body under the hydrate generation condition;
(3) after the reaction temperature is reduced to a temperature range of the hydrate self-protection effect below zero degree, the reaction pressure is slowly reduced to a pressure which is close to and slightly higher than the phase equilibrium pressure of the hydrate corresponding to the temperature; filling the adsorption-absorption agent into a reaction system, and forming an adsorption-absorption protective layer outside the hydrate protective layer;
(4) artificial thickening of the outer ice layer: when the temperature of the system is below the freezing point, a certain volume of water is injected into the reaction system, and a layer of ice layer is formed outside the adsorption-absorption protective layer.
Aiming at the problems in the prior art, the invention adopts multi-stage coupling to strengthen the stability of the hydrate structure, and covers a hydrate protective layer, an absorption-adsorption layer and a strengthened ice layer on the surface of a solid hydrate core body, thereby effectively reducing the decomposition rate of the inner layer hydrate and improving the stability of the hydrate structure.
In order to evaluate the technical effect of the invention, a high-pressure reaction kettle is adopted to carry out experiment and detection according to the following method:
(1) after the whole experimental system is cleaned, 10mL of aqueous solution of a hydrate accelerant is prepared according to the proportion and placed in a high-pressure reaction kettle body, firstly, the high-pressure reaction kettle is vacuumized, and experimental gas is introduced for replacing for more than 3 times; setting the system temperature as an experimental temperature, introducing a certain amount of experimental gas into the high-pressure reaction kettle to ensure that the system reaches the dissolution balance (the introduced gas pressure is less than the corresponding hydrate equilibrium pressure at the temperature, and the equilibrium pressure is calculated by adopting a Chen-Guo hydrate phase equilibrium equation model) after the temperature in the reaction kettle reaches a preset value and is stable for 2 hours, and then continuously introducing the high-pressure experimental gas to the pressure required by the experiment; in the experimental process, the pressure and the temperature of the high-pressure reaction kettle are kept constant, the stirring speed is adjusted to be 60r/min, and the experiment is started; observing the macroscopic morphological change in the system, and shooting on line by using a video recorder, wherein the pressure in the kettle is recorded by adopting an automatic data acquisition system along with the change of the reaction time; when the pressure in the kettle is not reduced for 2 hours continuously, the default solid hydrate nucleus is formed;
(2) filling a starch-based surfactant dispersion liquid with a certain concentration prepared in advance into the high-pressure reaction kettle through a high-pressure filling device, forming a hydrate protective layer on the surface of the solid hydrate core body under the conditions of temperature and pressure in the step (1), and completely forming a default hydrate protective layer when the pressure in the high-pressure reaction kettle is not obviously reduced within 2 hours;
(3) reducing the reaction temperature to a temperature range (253.15K-272.15K) with the self-protection effect of the hydrate below zero, and then slowly reducing the pressure of the reaction kettle to a pressure which is close to and slightly higher than the equilibrium pressure of the hydrate phase corresponding to the temperature; filling the adsorption-absorption agent into a reaction system through a high-pressure filling device to form an adsorption-absorption protective layer outside the hydrate protective layer;
(4) filling a certain volume of water into the high-pressure reaction kettle through a high-pressure filling device, and forming an ice layer with a certain thickness outside the adsorption-absorption protective layer again;
(5) and rapidly reducing the pressure in the reaction system to atmospheric pressure, rapidly closing an exhaust valve, recording the pressure change in the high-pressure reaction kettle within 18h of continuous decomposition in real time, and calculating the decomposition release amount of the hydrate according to the pressure change from atmospheric pressure to final pressure in the high-pressure reaction kettle.
The invention also provides an evaluation method for the technical effect after the method for enhancing the storage and transportation stability of the solid hydrate is adopted, which comprises the following steps: firstly, through the step (1), when the pressure in the kettle is not reduced for 2 hours continuously, the default hydrate formation is finished, and the gas consumption caused by the reduction of the pressure in the kettle in the experimental process is equal to the gas consumption in the kettle.
The gas consumption is as follows:
n c ＝n 0 -n t (1)
n c is the gas consumption of the gas in the reaction kettle at the time of t, n 0 Is the corresponding molar amount of gas in the system at the beginning of the experiment, n t The experiment was conducted until time t, and the molar amount of gas in the system was determined.
From the gas state equation, equation (1) can again be written as equation (2), where P 0 And P t For the system pressure, Z, at the induction time and time t, at which the experiment was carried out 0 And Z t The gas compression factor (calculated from Peng-Robinson equation of state) for the corresponding state is, V g The volume of gas phase space in the system, R is the gas constant, and T is the experimental temperature.
And (3) after the exhaust valve is closed in the step (5), continuing the experiment for 18h, converting the gas pressure in the system at the moment into the release amount of the decomposition gas through a Chen-Guo hydrate phase equilibrium equation, and taking the ratio of the release amount of the decomposition gas to the total consumption as the decomposition rate of the hydrate so as to evaluate the storage stability of the hydrate.
The Chen-Guo hydrate phase equilibrium model is a well-known calculation equation in the art, such as the Chen-Guo hydrate phase equilibrium equation model described in published journal of foreign languages, Chen G.J., Guo T.M.A new early to gas hydrate modification, Chen.Eng.J., 1998,71(2):145-151.
The test gas used in all of the comparative examples and examples described below was methane gas having a purity of 99.99%.
The present invention will be described in detail below by way of examples. In the following examples, graphene and carbon nanotubes were obtained from Nanjing Xiancheng nanomaterial science and technology, Inc., sodium carboxymethyl starch was obtained from Shanghai Aladdin Biotechnology, Inc., and alkyl polyglycoside surfactants were obtained from Shijiazhuang Jinmor Chemicals, Inc., where the detailed information of the different carbon chain length types is shown in Table 1.
TABLE 1
| Item | APG0814 | APG1214 | APG1216 |
| Appearance of the product | Yellowish viscous liquid | Yellowish viscous liquid | Yellowish viscous liquid |
| Content of solids/%) | 50 | 50 | 50 |
| pH (10% aqueous solution) | 11.5～12.5 | 11.5～12.5 | 11.5～12.5 |
| Content of free alcohol/%) | ≤1.0 | ≤1.0 | ≤1.0 |
| Inorganic salt content/%) | ≤4.0 | ≤4.0 | ≤4.0 |
| Low carbon glycoside content/%) | ≤0.5 | ≤0.5 | ≤0.5 |
| Average degree of polymerization | 1.2～1.8 | 1.2～1.8 | 1.2～1.8 |
| Viscosity (20 ℃ C.)/mPa.s | ≥1000 | ≥3000 | ≥3000 |
| Cloud Point/. degree.C | >100 | >100 | >100 |
| HLB value | 13～15 | 12～14 | 10～12 |
| Density of | 1.05～1.15 | 1.05～1.15 | 1.05～1.15 |
Example 1
Initial aqueous system of solid hydrate nuclei: the adopted hydrate accelerant is prepared from tetrahydrofuran and histidine according to the mass ratio of 1:1, and a water-containing system of 10mL is formed according to the mass ratio of the hydrate accelerant to water of 1: 100.
Dispersion containing starch-based surfactant: the composite is prepared from sodium carboxymethyl starch and alkyl polyglycoside APG1214 according to the mass ratio of 1: 2; and dispersing the starch-based surfactant into water according to the mass ratio of the starch-based surfactant to the water of 1:100 to obtain 1mL of dispersion liquid containing the starch-based surfactant.
Adsorption-absorbent: the mass ratio of graphene to n-undecane is 2:100 was prepared as 1mL of an adsorbent-absorbent.
The volume of pure water for ice making was 0.5 mL.
The specific experimental steps are as follows:
(1) and (3) forming solid hydrate nuclei, wherein the experiment temperature and the experiment pressure are 276.15K and 7.0MPa respectively, the pressure and the temperature in the reaction kettle are kept constant in the experiment process, and when the pressure is not reduced for 2 hours continuously, the formation of the hydrate nuclei is finished by default.
The gas consumption in the kettle during the experiment was 92 mmol.
(2) And (2) injecting a dispersion liquid containing a starch-based surfactant prepared in advance into the reaction kettle by using a high-pressure injection device, forming a hydrate protective layer on the surface of a solid hydrate nucleus under the conditions of forming temperature and pressure of the solid hydrate nucleus of 276.15K and 7.0MPa, and completely forming the default hydrate protective layer when the pressure in the reaction kettle is not obviously reduced within 2.0 h.
(3) After the reaction temperature is reduced to below zero DEG C, the self-protection effect temperature range of the hydrate is 268.15K, the kettle pressure is slowly reduced to be close to and slightly higher than the phase equilibrium pressure (0.85MPa) of the hydrate corresponding to the temperature; and (3) filling the adsorption-absorption agent prepared in advance into a reaction system through a high-pressure filling device, and forming an adsorption-absorption protective layer outside the hydrate protective layer.
(4) And filling pure water into the reaction kettle through a high-pressure filling device, and forming an ice layer outside the adsorption-absorption protective layer again. And then, quickly reducing the pressure in the reaction system to the atmospheric pressure, quickly closing an exhaust valve, recording the pressure change in the reaction kettle within 18h of continuous decomposition in real time, and calculating the decomposition release amount of the hydrate to be 6mmol according to the pressure change from the atmospheric pressure to the final pressure in the reaction kettle, wherein the decomposition rate of the hydrate is only 6.52%.
Example 2
Initial aqueous system of solid hydrate nuclei: the adopted hydrate accelerant is prepared from tetrahydrofuran and histidine according to the mass ratio of 1:1, and a water-containing system of 10mL is formed according to the mass ratio of the hydrate accelerant to water of 3: 100.
The dispersion containing the starch-based surfactant was the same as in example 1.
The absorber-absorber was the same as in example 1.
The volume of pure water for ice making layer was 0.4 mL.
The specific experimental procedure was the same as in example 1, wherein the gas consumption in the kettle during the experiment for the formation of solid hydrate nuclei in step (1) was 96 mmol.
And recording the pressure change in the reaction kettle within 18h of continuous decomposition in real time, and calculating the decomposition release amount of the hydrate to be 5.2mmol according to the pressure change from the atmospheric pressure to the final pressure in the reaction kettle, wherein the decomposition rate of the hydrate is only 5.47%.
Example 3
Initial aqueous system of solid hydrate nuclei: the adopted hydrate accelerant is prepared from tetrahydrofuran and leucine according to the mass ratio of 1:1, and a water-containing system of 10mL is formed according to the mass ratio of the hydrate accelerant to water of 2: 100.
Dispersion containing starch-based surfactant: the starch-based surfactant is prepared from sodium carboxymethyl starch and alkyl polyglycoside APG0814 according to the mass ratio of 1:2, and is dispersed in water according to the mass ratio of 1:100 of a starch-based surfactant to water to obtain 1mL of dispersion liquid containing the starch-based surfactant.
Adsorption-absorbent: the mass ratio of the carbon nano tube to the n-undecane is 2:100 was prepared as 1mL of an adsorbent-absorbent.
The volume of pure water for ice making layer was 0.5 mL.
The specific experimental procedure was the same as in example 1, wherein the gas consumption in the kettle during the experiment for the formation of solid hydrate nuclei in step (1) was 93 mmol.
And recording the pressure change in the reaction kettle within 18h of continuous decomposition in real time, and calculating the decomposition release amount of the hydrate to be 8mmol according to the pressure change from the atmospheric pressure to the final pressure in the reaction kettle, wherein the decomposition rate of the hydrate is 8.61%.
Example 4
Initial aqueous system of solid hydrate nuclei: the adopted hydrate accelerant is prepared from tetrahydrofuran and leucine according to the mass ratio of 1:1, and a water-containing system of 10mL is formed according to the mass ratio of the hydrate accelerant to water of 4: 100.
Dispersion containing starch-based surfactant: the starch-based surfactant is prepared from sodium carboxymethyl starch and alkyl polyglycoside APG1214 according to the mass ratio of 1:2, and is dispersed in water according to the mass ratio of 1:100 of the starch-based surfactant to the water to obtain 1mL of dispersion liquid containing the starch-based surfactant.
Adsorption-absorbent: the mass ratio of the carbon nano tube to the n-undecane is 2:100 was prepared as 1mL of an adsorbent-absorbent.
The volume of pure water for ice making layer was 0.5 mL.
The specific experimental procedure was the same as in example 1, wherein the amount of gas consumed in the kettle during the experiment for the formation of a solid hydrate nucleus in step (1) was 96 mmol.
And recording the pressure change in the reaction kettle within 18h of continuous decomposition in real time, and calculating the decomposition release amount of the hydrate to be 4.8mmol according to the pressure change from the atmospheric pressure to the final pressure in the reaction kettle, wherein the decomposition rate of the hydrate is 5.0%.
Example 5
Initial aqueous system of solid hydrate nuclei: the adopted hydrate accelerant is prepared from tetrabutylammonium bromide and leucine according to the mass ratio of 1:1, and a water-containing system of 10mL is formed according to the mass ratio of the hydrate accelerant to water of 4: 100.
Dispersion containing starch-based surfactant: the starch-based surfactant is prepared from sodium carboxymethyl starch and alkyl polyglycoside APG1214 according to the mass ratio of 1:2, and is dispersed in water according to the mass ratio of 1:100 of the starch-based surfactant to the water to obtain 1mL of dispersion liquid containing the starch-based surfactant.
Adsorption-absorbent: the mass ratio of the carbon nano tube to the decane is 2:100 was prepared as 1mL of an adsorbent-absorbent.
The volume of pure water for ice making was 0.5 mL.
The specific experimental procedure was the same as in example 1, wherein the amount of gas consumed in the kettle during the experiment for the formation of a solid hydrate nucleus in step (1) was 91 mmol.
And recording the pressure change in the reaction kettle within 18h of continuous decomposition in real time, and calculating the decomposition release amount of the hydrate to be 6.2mmol and the decomposition rate of the hydrate to be 6.81% according to the pressure change from the atmospheric pressure to the final pressure in the reaction kettle.
Example 6
Initial aqueous system of solid hydrate nuclei: the adopted hydrate accelerant is prepared from tetrabutylammonium bromide and leucine according to the mass ratio of 1:1, and a water-containing system of 10mL is formed according to the mass ratio of the hydrate accelerant to water of 3: 100.
Dispersion containing starch-based surfactant: the starch-based surfactant is prepared from sodium carboxymethyl starch and alkyl polyglycoside APG1214 according to the mass ratio of 1:2, and is dispersed in water according to the mass ratio of 1:100 of the starch-based surfactant to the water to obtain 1mL of dispersion liquid containing the starch-based surfactant.
Adsorption-absorbent: the mass ratio of the carbon nano tube to the decane is 2:100 was prepared as 1mL of adsorbent-absorbent.
The volume of pure water for ice making layer was 0.5 mL.
The specific experimental procedure was the same as in example 1, wherein the gas consumption in the kettle during the experiment for the formation of solid hydrate nuclei in step (1) was 89 mmol.
And recording the pressure change in the reaction kettle within 18h of continuous decomposition in real time, and calculating the decomposition release amount of the hydrate to be 5.2mmol and the decomposition rate of the hydrate to be 5.84% according to the pressure change from the atmospheric pressure to the final pressure in the reaction kettle.
Example 7
A coupled enhanced solid hydrate was prepared using the initial aqueous system forming solid hydrate nuclei and the dispersion containing the starch-based surfactant of example 1, except that only steps (1) and (2) were performed, and steps (3) through (4) were not performed.
The gas consumption in the reactor in the step (1) was 92 mmol.
And then, quickly reducing the pressure in the reaction system to the atmospheric pressure, quickly closing an exhaust valve, recording the pressure change in the reaction kettle within 18h of continuous decomposition in real time, and calculating the decomposition release amount of the hydrate to be 12.49mmol and the decomposition rate of the hydrate to be 13.58% according to the pressure change from the atmospheric pressure to the final pressure in the reaction kettle.
Example 8
A coupled enhanced solid hydrate was prepared as in example 7, except that the alkylpolyglycoside APG1214 in example 7 was replaced with alkylpolyglycoside APG 1216.
In the step (1), the amount of gas consumed in the reaction vessel was 92 mmol.
And then, quickly reducing the pressure in the reaction system to atmospheric pressure, quickly closing an exhaust valve, recording the change of the pressure in the reaction kettle within 18h of continuous decomposition in real time, and calculating the decomposition release amount of the hydrate to be 14.55mmol and the decomposition rate of the hydrate to be 15.81% according to the change of the pressure in the reaction kettle from atmospheric pressure to final pressure.
Example 9
A coupling-enhanced solid hydrate was prepared using the formulation and method of example 7, except that the starch-based surfactant was included in a 1:0.3 mass ratio of sodium carboxymethyl starch to alkyl polyglycoside APG 1214.
The gas consumption in the reactor in the step (1) was 92 mmol.
And then, quickly reducing the pressure in the reaction system to the atmospheric pressure, quickly closing an exhaust valve, recording the pressure change in the reaction kettle within 18h of continuous decomposition in real time, and calculating the decomposition release amount of the hydrate to be 15.05mmol and the decomposition rate of the hydrate to be 16.35% according to the pressure change from the atmospheric pressure to the final pressure in the reaction kettle.
Example 10
A coupling-enhanced solid hydrate was prepared using the formulation and method of example 7, except that the starch-based surfactant was included in a 1:4 by mass ratio of sodium carboxymethyl starch to alkyl polyglycoside APG 1214.
The consumption of the gas in the kettle in the step (1) is 92 mmol.
And then, quickly reducing the pressure in the reaction system to the atmospheric pressure, quickly closing an exhaust valve, recording the pressure change in the reaction kettle within 18h of continuous decomposition in real time, and calculating the decomposition release amount of the hydrate to be 14.06mmol and the decomposition rate of the hydrate to be 15.28% according to the pressure change from the atmospheric pressure to the final pressure in the reaction kettle.
Example 11
Hydrates were prepared using the initial aqueous system forming solid hydrate nuclei, the dispersion containing the starch-based surfactant and the adsorption-absorption agent of example 1, except that only step (1), step (2) and step (3) were carried out, and step (4) was not carried out.
The gas consumption in the reactor in the step (1) was 92 mmol.
And then, quickly reducing the pressure in the reaction system to the atmospheric pressure, quickly closing an exhaust valve, recording the pressure change in the reaction kettle within 18h of continuous decomposition in real time, and calculating the decomposition release amount of the hydrate to be 10.33mmol and the decomposition rate of the hydrate to be 11.23% according to the pressure change from the atmospheric pressure to the final pressure in the reaction kettle.
Example 12
The formula and the method in example 11 were used to prepare a coupled enhanced solid hydrate, except that the mass ratio of graphene to n-undecane in the adsorption-absorption agent was 12: 100.
the consumption of the gas in the kettle in the step (1) is 92 mmol.
And then, quickly reducing the pressure in the reaction system to the atmospheric pressure, quickly closing an exhaust valve, recording the pressure change in the reaction kettle within 18h of continuous decomposition in real time, and calculating the decomposition release amount of the hydrate to be 10.89mmol and the decomposition rate of the hydrate to be 11.84% according to the pressure change from the atmospheric pressure to the final pressure in the reaction kettle.
Example 13
The formula and the method in example 11 were used to prepare a coupled enhanced solid hydrate, except that the mass ratio of graphene to n-undecane in the adsorption-absorption agent was 0.3: 100.
the amount of gas consumed in the reactor in step (1) was 92 mmol.
And then, quickly reducing the pressure in the reaction system to the atmospheric pressure, quickly closing an exhaust valve, recording the change of the pressure in the reaction kettle within 18h of continuous decomposition in real time, and calculating the decomposition release amount of the hydrate to be 11.12mmol and the decomposition rate of the hydrate to be 12.09% according to the change of the pressure in the reaction kettle from the atmospheric pressure to the final pressure.
Example 14
A coupled enhanced solid hydrate was prepared using the formulation and method of example 1, except that the amount of water added in step (4) was 1 mL.
The gas consumption in the reactor in the step (1) was 92 mmol.
And then, quickly reducing the pressure in the reaction system to the atmospheric pressure, quickly closing an exhaust valve, recording the pressure change in the reaction kettle within 18h of continuous decomposition in real time, and calculating the decomposition release amount of the hydrate to be 9.81mmol and the decomposition rate of the hydrate to be 10.67% according to the pressure change from the atmospheric pressure to the final pressure in the reaction kettle.
Comparative example 1
Hydrates were prepared using the initial aqueous system of example 1 which formed solid hydrate nuclei except that only step (1) was carried out, and steps (2) to (4) were not carried out.
The amount of gas consumed in the reactor in step (1) was 92 mmol.
And then, quickly reducing the pressure in the reaction system to the atmospheric pressure, quickly closing an exhaust valve, recording the pressure change in the reaction kettle within 18h of continuous decomposition in real time, and calculating the decomposition release amount of the hydrate to be 25mmol according to the pressure change from the atmospheric pressure to the final pressure in the reaction kettle, wherein the decomposition rate of the hydrate is 27.17%.
Comparative example 2
A coupling-enhanced solid hydrate was prepared using the formulation and method of example 7, except that only sodium carboxymethyl starch was added to the dispersion containing the starch-based surfactant and dispersed in water at a sodium carboxymethyl starch to water mass ratio of 1:100 to yield 1mL of the dispersion containing the starch-based surfactant.
The consumption of the gas in the kettle in the step (1) is 92 mmol.
And then, quickly reducing the pressure in the reaction system to the atmospheric pressure, quickly closing an exhaust valve, recording the pressure change in the reaction kettle within 18h of continuous decomposition in real time, and calculating the decomposition release amount of the hydrate to be 17.37mmol and the decomposition rate of the hydrate to be 18.88% according to the pressure change from the atmospheric pressure to the final pressure in the reaction kettle.
Comparative example 3
A coupling-enhanced solid hydrate was prepared using the formulation and method of example 7, except that only the alkylpolyglycoside APG1214 was added to the dispersion containing the starch-based surfactant and dispersed in water at a mass ratio of alkylpolyglycoside APG1214 to water of 1:100 to give 1mL of the dispersion containing the starch-based surfactant.
The gas consumption in the reactor in the step (1) was 92 mmol.
And then, quickly reducing the pressure in the reaction system to the atmospheric pressure, quickly closing an exhaust valve, recording the change of the pressure in the reaction kettle within 18h of continuous decomposition in real time, and calculating the decomposition release amount of the hydrate to be 17.86mmol and the decomposition rate of the hydrate to be 19.42% according to the change of the pressure in the reaction kettle from the atmospheric pressure to the final pressure.
The preferred embodiments of the present invention have been described above in detail, but the present invention is not limited thereto. Within the scope of the technical idea of the invention, many simple modifications can be made to the technical solution of the invention, including combinations of various technical features in any other suitable way, and these simple modifications and combinations should also be regarded as the disclosure of the invention, and all fall within the scope of the invention.
Claims (31)
1. A hydrate decomposition inhibiting composition is characterized by comprising a starch-based surfactant and an adsorption-absorption agent which is stored independently of the starch-based surfactant, wherein the mass ratio of the starch-based surfactant to the adsorption-absorption agent is 0.5-10:1, the adsorption-absorption agent comprises a porous adsorption material and multi-carbon straight-chain alkane, the starch-based surfactant comprises sodium carboxymethyl starch and alkyl glycoside surfactants, the mass ratio of the sodium carboxymethyl starch to the alkyl glycoside surfactants is 1:1-3, the porous adsorption material is at least one of expanded graphite, nano graphite, carbon nano tubes, graphene, an ordered mesoporous molecular sieve and a metal organic framework material, and the multi-carbon straight-chain alkane is straight-chain alkane containing 5-15 carbon atoms.
2. The hydrate decomposition inhibiting composition according to claim 1, wherein the mass ratio of the sodium carboxymethyl starch to the alkyl glycoside surfactant is 1:1.5 to 2.5.
3. The hydrate decomposition inhibiting composition according to claim 1 or 2, wherein the alkyl glycoside surfactant has a molecular structure of RO (G) n R is C 8 -C 18 Straight chain or branched chain alkyl, G represents sugar unit, n represents the number of the sugar unit, wherein n is a positive integer of 1-3.
4. The hydrate decomposition inhibiting composition according to claim 3, wherein the alkyl glycoside surfactant is at least one of APG0810, APG0814, APG1214, APG0816, and APG 1216.
5. The hydrate decomposition inhibiting composition according to claim 1, wherein a mass ratio of the porous adsorbing material to the multi-carbon linear alkane is 0.5-10: 100.
6. The hydrate decomposition inhibiting composition according to claim 5, wherein the mass ratio of the porous adsorbing material to the multi-carbon linear alkane is 1-5: 100.
7. the hydrate decomposition inhibiting composition according to claim 1, wherein the multi-carbon linear alkane is at least one of n-hexane, n-heptane, n-octane, n-nonane, n-decane, and n-undecane.
8. A coupled enhanced solid hydrate comprising a solid hydrate core and a hydrate protective layer coating the solid hydrate core;
the hydrate protective layer contains a starch-based surfactant, the starch-based surfactant consists of sodium carboxymethyl starch and an alkyl glycoside surfactant, and the mass ratio of the sodium carboxymethyl starch to the alkyl glycoside surfactant is 1: 1-3;
the solid hydrate nuclei are obtained in the following manner: methane gas is contacted with a hydrate promoter in an aqueous system containing the hydrate promoter under solid hydrate forming conditions.
9. The coupling-enhanced solid hydrate of claim 8, wherein the mass ratio of sodium carboxymethyl starch to alkyl glycoside surfactant is 1: 1.5-2.5.
10. The coupling-enhanced solid hydrate of claim 8, further comprising an adsorption-absorption protective layer coated over said hydrate protective layer; the adsorption-absorption protective layer contains an adsorption-absorption agent.
11. The coupled enhanced solid hydrate of claim 10, wherein the adsorption-absorption agent comprises a porous adsorption material and a multi-carbon linear alkane, wherein the porous adsorption material is at least one of expanded graphite, nano graphite, carbon nano tubes, graphene, an ordered mesoporous molecular sieve and a metal organic framework material, and the multi-carbon linear alkane is a linear alkane containing 5-15 carbon atoms.
12. The coupling-enhanced solid hydrate of claim 11, wherein the mass ratio of the porous adsorbent material to the multi-carbon linear alkane is 0.5-10: 100.
13. The coupled enhanced solid hydrate of claim 12, wherein the mass ratio of the porous adsorbent material to the multi-carbon linear alkane is 1-5: 100.
14. the coupled enhanced solid hydrate of any one of claims 10-13, further comprising a layer of ice coated outside the adsorption-absorption protective layer.
15. A method for enhancing storage and transportation stability of solid hydrates, the method comprising: after the solid hydrate core is formed, adding a dispersion liquid containing a starch-based surfactant to a system containing the solid hydrate core under the solid hydrate generating conditions to form a hydrate protective layer coating the solid hydrate core outside the solid hydrate core;
wherein the starch-based surfactant consists of sodium carboxymethyl starch and an alkyl glycoside surfactant, and the mass ratio of the sodium carboxymethyl starch to the alkyl glycoside surfactant is 1: 1-3;
the solid hydrate nuclei are obtained in the following manner: methane gas is contacted with a hydrate promoter in an aqueous system containing the hydrate promoter under solid hydrate forming conditions.
16. The method according to claim 15, wherein the mass ratio of the sodium carboxymethyl starch to the alkyl glycoside surfactant is 1: 1.5-2.5.
17. The method of claim 16, wherein the mass ratio of starch-based surfactant to dispersion is 0.5-10: 100.
18. The method of claim 17, wherein the mass ratio of starch-based surfactant to dispersion is 1-5: 100.
19. the method according to claim 15, wherein the volume ratio of the dispersion containing the starch-based surfactant to the initial aqueous system forming solid hydrate nuclei does not exceed 15: 100.
20. The method of claim 19 wherein the volume ratio of the dispersion containing the starch-based surfactant to the initial aqueous system forming solid hydrate nuclei is from 6 to 12: 100.
21. the method of claim 15, further comprising adding an adsorption-absorption agent to the system after forming the hydrate protective layer under conditions where the solid hydrate is in a self-protecting effect temperature range and the system pressure is near to and above the phase equilibrium pressure of the hydrate in the temperature range to form an adsorption-absorption protective layer over the hydrate protective layer.
22. The method of claim 21, wherein the adsorption-absorption agent comprises a porous adsorption material and a multi-carbon linear alkane, wherein the porous adsorption material is at least one of expanded graphite, nanographite, a carbon nanotube, graphene, an ordered mesoporous molecular sieve and a metal organic framework material, and the multi-carbon linear alkane is a linear alkane containing 5 to 15 carbon atoms.
23. The method of claim 22, wherein the mass ratio of the porous adsorbent material to the multi-carbon linear alkane is 0.5-10: 100.
24. The method of claim 23, wherein the mass ratio of the porous adsorbent material to the multi-carbon linear alkane is 1-5: 100.
25. the method of claim 24, wherein the solid hydrate self-protective effect temperature range is 253.15K-272.15K.
26. The method of claim 23 wherein the hydrate phase equilibrium pressure over the self-protective effect temperature range is equal to the pressure calculated by the Chen-Guo hydrate phase equilibrium equation.
27. A method as claimed in claim 21 wherein the volume ratio of adsorbent-absorbent to initial aqueous system forming the solid hydrate nuclei does not exceed 15: 100.
28. A method as claimed in claim 27 wherein the volume ratio of adsorbent-absorbent to initial aqueous system forming the solid hydrate nuclei is from 5 to 10: 100.
29. the method according to claim 21 or 22, further comprising adding water to the system after the formation of the adsorption-absorption protective layer at a temperature below the freezing point of the system to form an ice layer covering the adsorption-absorption protective layer outside the adsorption-absorption protective layer.
30. A method as claimed in claim 29 wherein the volume ratio of water added to form the ice layer to the initial aqueous system forming the solid hydrate nuclei does not exceed 5: 100.
31. A method as claimed in claim 30 wherein the volume ratio of water added to form the ice layer to the initial aqueous system forming the solid hydrate nuclei is from 2 to 4: 100.
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