CN117160376A

CN117160376A - Ice medium for accelerating generation of gas hydrate, and preparation method and application thereof

Info

Publication number: CN117160376A
Application number: CN202311089005.1A
Authority: CN
Inventors: 肖朋; 陈光进; 孙长宇; 李娟娟
Original assignee: China University of Petroleum Beijing
Current assignee: China University of Petroleum Beijing
Priority date: 2023-08-28
Filing date: 2023-08-28
Publication date: 2023-12-05

Abstract

The invention provides an ice medium for accelerating gas hydrate generation, a preparation method and application thereof, wherein the ice medium comprises ice powder and a surfactant uniformly distributed in the ice powder, or comprises the ice powder, the surfactant uniformly distributed in the ice powder and a thermodynamic inhibitor, the mass fraction of the surfactant in the ice medium is more than 400ppm, the mass fraction of the thermodynamic inhibitor in the ice medium is less than C/5, and C is the mass fraction of a thermodynamic inhibitor aqueous solution taking the use temperature of the ice medium as a freezing point. When the temperature is lower than 0 ℃, the ice medium is used for generating gas hydrate, and the water conversion rate higher than 80% can be obtained within 5min, so that the defects of low speed, low gas storage amount, large heat release and the like existing in the process of generating the gas hydrate by adopting the prior art can be overcome; the preparation method of the ice medium is simple, low in energy consumption, low in cost and wide in temperature application range, and can be used in the fields of gas storage and transportation, gas separation and the like.

Description

Ice medium for accelerating generation of gas hydrate, and preparation method and application thereof

Technical Field

The invention relates to an ice medium for accelerating generation of gas hydrate, and a preparation method and application thereof, and belongs to the technical field of gas hydrate.

Background

Gas hydrates are ice-like solids produced by gas small molecules and water molecules at low temperature and high pressure. The gas small molecules capable of generating gas hydrate comprise methane, ethane, propane, carbon dioxide, hydrogen sulfide and the like. The water molecules that form the gas hydrate may be provided by liquid water or by solid ice. Gas hydrates are not only in the form of natural gas hydrates which are largely available on the sea floor or in permafrost zones, but also are a potential energy source of importance, and are potential alternatives to some industrial technologies due to important physicochemical properties. Each volume of gas hydrate can store about 180 standard volumes of natural gas and can be stored at normal pressure below-5 ℃; meanwhile, the temperature and pressure conditions required by different gases to form gas hydrates are different; thus, the gas hydrates can be used for natural gas storage and gas separation.

The formation of gas hydrates is the basis for the use of gas hydrates in the aforementioned industrial fields. However, gas hydrates under unmanned intervention typically form dense hydrate films at the gas-water interface, impeding contact of unconverted gas molecules with water molecules, resulting in hydrate formation times as long as days to months. To date, various techniques have been developed to accelerate gas hydrate formation, including mechanical agitation, the use of kinetic promoters (surfactants, amino acids, starches, etc.), the use of dispersions (bubbling, spraying, fixed bed of aqueous porous media, water-in-oil emulsions, ice powders, etc.). Among them, the kinetic promoter is most preferable. In small laboratory scale production, kinetic promoters can reduce gas hydrate production times to about half an hour. However, kinetic promoters can cause gas hydrates to grow along the walls of the reactor, and when a certain amount of solution in the reactor is reached, the adherently growing hydrates can block the gas inlet and outlet holes, affecting the actual production operation. Meanwhile, when the hydrate is generated from the dynamic accelerator solution, the time consumption for generating the hydrate is obviously increased when the scale is enlarged due to the small gas-liquid interface. In addition, the heat release of gas hydrate generated from liquid water is large, and a large amount of foam can be generated when the generated hydrate is decomposed, so that the generation of the gas hydrate and the re-release of the gas can be respectively influenced.

The formation of hydrates from ice also accelerates the formation of gas hydrates to some extent, which has the advantage that less heat is generated when the hydrates are formed than in liquid water. The paper published by Kawamura et al (Journal of Crystal Growth,2002, 220-226) shows that when gas hydrates are formed in an ice powder having an average particle size of 9 μm, it takes at least 150 minutes to achieve a water conversion of 65% or more, indicating a slow rate of gas hydrates being formed directly in the ice powder. CN 112521994a discloses a fast hydrate formation medium, a preparation method, an application and a use method thereof, the method reduces the temperature of gas hydrate generated in a kinetic promoter solution to below 0 ℃ to decompose, ice obtained by decomposition is used for generating gas hydrate, so that the problem that the hydrate is slowly generated in ice can be solved, and meanwhile, desorption at a temperature below the freezing point can solve the problem of foaming when the hydrate containing the kinetic promoter is regasified. However, the preparation process of the method is complicated, and the ice obtained by decomposing the generated gas hydrate is reused for generating the gas hydrate, so that the comprehensive energy consumption is high. Meanwhile, the preparation of the medium utilizes a kinetic promoter solution to generate hydrate, and the problems that an air inlet and an air outlet are blocked by the hydrate and the hydrate is stripped from the wall surface of a reaction kettle cannot be avoided in large-scale preparation. In addition, the efficient use temperature range of the ice medium is too narrow, which is not beneficial to practical use.

Therefore, providing a novel ice medium for accelerating the generation of gas hydrate, and a preparation method and application thereof have become a technical problem to be solved in the art.

Disclosure of Invention

In order to solve the above-described drawbacks and disadvantages, an object of the present invention is to provide an ice medium for accelerating the formation of gas hydrates.

It is still another object of the present invention to provide a method of preparing the above ice media for accelerating gas hydrate formation.

It is a further object of the present invention to provide the use of the above described ice media for accelerating gas hydrate formation.

It is a further object of the present invention to provide a method for accelerating the formation of gas hydrates which uses the above described ice medium for accelerating the formation of gas hydrates.

In order to achieve the above object, in one aspect, the present invention provides an ice medium for accelerating gas hydrate formation, wherein the ice medium comprises ice powder and a surfactant uniformly distributed in the ice powder, or the ice medium comprises ice powder and a surfactant and a thermodynamic inhibitor uniformly distributed in the ice powder, and the surfactant accounts for more than 400ppm by mass of the ice medium, and the thermodynamic inhibitor accounts for less than C/5 by mass of the ice medium, wherein C is the mass fraction of a thermodynamic inhibitor aqueous solution taking the use temperature of the ice medium as a freezing point, and is expressed in wt%.

Here, sodium chloride is taken as an example of a thermodynamic inhibitor, and how to control the mass fraction of the thermodynamic inhibitor in the ice medium is described. The freezing point of the aqueous solution of sodium chloride with the mass fraction C of 10wt% is about-6.6 ℃, namely the mass fraction of the aqueous solution of sodium chloride with the freezing point of-6.6 ℃ is 10wt%, and when the ice medium needs to be made into hydrate at-6.6 ℃ (the use temperature of the ice medium), the mass content of sodium chloride in the ice medium is lower than 2wt%.

In the invention, the surfactant is a surfactant which can lower the freezing point of local water and can accelerate the generation of gas hydrate. As a specific embodiment of the ice medium according to the present invention, the surfactant includes one or more of sodium dodecyl sulfate, ammonium dodecyl sulfate, sodium dodecyl benzene sulfonate, dodecyl benzene sulfonic acid, sodium dodecyl sulfonate, sodium laurate, and the like;

preferably, the surfactant comprises one or a combination of a plurality of sodium dodecyl sulfate, ammonium dodecyl sulfate, sodium dodecyl benzene sulfonate, sodium laurate and the like.

In the invention, the thermodynamic inhibitor is a salt or alcohol substance capable of lowering the freezing point of water. As a specific embodiment of the ice medium according to the present invention, the thermodynamic inhibitor includes one or a combination of several of sodium chloride, potassium chloride and ethylene glycol. The surfactant, or the surfactant and the thermodynamic inhibitor uniformly distributed in the ice medium can form high-concentration sites on microcosmic parts, ice near the sites melts and forms an aqueous solution, and the thermodynamic inhibitor can overcome the defect that the surfactant reduces the local freezing point effect when the temperature is too low.

As a specific embodiment of the above ice medium of the present invention, the particle size of the ice powder is less than 300 μm.

In another aspect, the present invention also provides a method for preparing the ice medium for accelerating the formation of gas hydrate, wherein the preparation method comprises uniformly distributing a surfactant or a surfactant and a thermodynamic inhibitor in ice powder to form the ice medium, and the method specifically comprises:

preparing a surfactant aqueous solution or a surfactant and thermodynamic inhibitor aqueous solution, freezing the surfactant aqueous solution or the surfactant and thermodynamic inhibitor aqueous solution into ice cubes, and then crushing the ice cubes into ice powder to obtain the ice medium;

or freezing pure water to form ice cubes, crushing the ice cubes into ice powder, and uniformly mixing a surfactant and the ice powder, or uniformly mixing a surfactant, a thermodynamic inhibitor and the ice powder to obtain the ice medium;

or uniformly mixing natural snowflake with a surfactant or a surfactant with a thermodynamic inhibitor to obtain the ice medium.

In yet another aspect, the present invention also provides the use of an ice medium as described above for accelerating the formation of gas hydrates.

In yet another aspect, the present invention further provides a method for accelerating the formation of gas hydrates, wherein the method uses the ice medium for accelerating the formation of gas hydrates described above, and the method comprises:

firstly, filling the ice medium into a reactor precooled to be less than 0 ℃, ensuring that the temperature of the ice medium is less than 0 ℃ in the filling process so as to avoid melting of the ice medium, then adjusting the temperature of the ice medium to be the use temperature of less than 0 ℃ by utilizing a temperature control device, and then introducing gas for generating hydrate into the reactor, wherein the gas hydrate is generated by the ice medium and the gas.

As a specific embodiment of the above method of the present invention, the method specifically includes:

when the use temperature of the ice medium is higher than-1.5 ℃ and lower than 0 ℃, the ice medium comprises ice powder and surfactant uniformly distributed in the ice powder; filling the ice medium into a reactor precooled to a temperature higher than-1.5 ℃ and lower than 0 ℃, then adjusting the temperature of the ice medium to a use temperature higher than-1.5 ℃ and lower than 0 ℃ by utilizing a temperature control device, and then introducing gas for generating hydrate into the reactor to generate gas hydrate;

or when the use temperature of the ice medium is not higher than-1.5 ℃ and the gas temperature for hydrate formation is lower than 0 ℃, the ice medium comprises ice powder, and surfactant and thermodynamic inhibitor uniformly distributed in the ice powder; filling the ice medium into a reactor precooled to the temperature not higher than-1.5 ℃, then adjusting the temperature of the ice medium to the use temperature not higher than-1.5 ℃ by utilizing a temperature control device, and then introducing gas for generating hydrate with the temperature lower than 0 ℃ into the reactor to generate gas hydrate;

Or when the use temperature of the ice medium is not higher than-1.5 ℃ and the gas temperature for hydrate formation is higher than 0 ℃, the ice medium comprises ice powder and surfactant uniformly distributed in the ice powder, or the ice medium comprises ice powder and surfactant and thermodynamic inhibitor uniformly distributed in the ice powder; and (3) loading the ice medium into a reactor precooled to the temperature not higher than-1.5 ℃, then adjusting the temperature of the ice medium to the use temperature not higher than-1.5 ℃ by utilizing a temperature control device, and then introducing gas for generating hydrate with the temperature higher than 0 ℃ into the reactor to generate gas hydrate.

In the above method of the present invention, when the use temperature of the ice medium is not higher than-1.5 ℃, the gas temperature for hydrate formation is not as high as possible. The hot gas acts to raise the surface temperature of the ice media particles to melt a portion of the aqueous solution as an initial point of growth for the hydrates. If the gas temperature is too high, for example 200-300 ℃, too much liquid is melted at this time, so that the reaction contact surface of the gas and water becomes smaller, and the hydrate generation rate is reduced; if the gas temperature is too low, this may result in too little water being melted out, or freezing again immediately, and may also result in poor results.

As a specific embodiment of the above method of the present invention, wherein when the gas for hydrate formation having a temperature higher than 0 ℃ is supplied to the ice medium with sufficient heat to melt not less than 0.25wt% of the ice powder (based on the total weight of the ice powder), and the melted solution is kept in a non-frozen state for 5 minutes after the gas pressure for hydrate formation has reached the hydrate formation pressure corresponding to the use temperature of the ice medium, the ice medium comprises the ice powder and the surfactant uniformly distributed in the ice powder. If the gas for hydrate formation at a temperature above 0 ℃ does not provide enough heat to meet the above conditions, then the ice powder needs to be added with a thermodynamic inhibitor, i.e. the ice medium comprises ice powder and a surfactant and thermodynamic inhibitor uniformly distributed in the ice powder.

In the actual use process, the winter ambient temperature of a part of areas is lower than 0 ℃, at the moment, the ice medium composition suitable for the ambient temperature is selected only according to the ambient temperature, the ice medium composition is directly filled into a reactor with the same ambient temperature, and then gas for generating hydrate is introduced into the reactor, so that the ice medium and the gas generate gas hydrate.

In the invention, the surfactant in the ice medium can reduce the freezing point of local water in the ice medium, namely, a small amount of uniformly distributed surfactant aqueous solution can be formed in the ice medium. At temperatures below-1.5 c, it has been difficult for the surfactant contained in the ice medium to produce sufficient aqueous solution in the ice medium, and the addition of small amounts of thermodynamic inhibitors to the ice medium may compensate for this deficiency. In addition, the higher temperature gas used for hydrate formation may also produce an aqueous solution on the surface of the ice media particles at a temperature below-1.5 ℃, but correspondingly, the concentration of the thermodynamic inhibitor needs to be reduced to reduce the effect of the thermodynamic inhibitor on hydrate formation. The aqueous solution may provide an initial point of formation for hydrate formation below freezing.

As a specific embodiment of the above method of the present invention, the gas for hydrate formation includes one or a combination of several of methane, ethane, propane, carbon dioxide, and hydrogen sulfide.

As a specific embodiment of the above method of the present invention, if the gas for hydrate formation is a pure component gas, the gas pressure needs to be maintained higher than the formation pressure of the hydrate of the gas at the use temperature of the ice medium; if the gas used for generating the hydrate is a mixed gas, the partial pressure of the gas component which is easy to form the hydrate in the mixed gas is kept higher than the generation pressure of the hydrate of the gas component which is easy to form the hydrate at the using temperature of the ice medium.

As a specific embodiment of the above method of the present invention, the method further includes: in the gas hydrate generation process, refrigeration measures are taken to remove heat generated in the hydrate generation process.

As a specific embodiment of the method of the present invention, the temperature of the ice medium for accelerating the formation of gas hydrate is maintained below 0 ℃ after the completion of the preparation until the ice medium contacts the gas for hydrate formation and forms gas hydrate.

In the method for accelerating the generation of the gas hydrate, the reactor, the temperature control device and the like are all conventional equipment and can be reasonably selected according to the needs. For example, in some embodiments of the invention, the reactor is an autoclave.

Compared with the prior art, the invention has the following beneficial technical effects:

according to the invention, the characteristic that the freezing point of part of the high-concentration surfactant solution is reduced is utilized, when the surfactant is uniformly distributed in the ice powder, the tiny area near the surfactant is a high-concentration site, so that a local surfactant solution can be formed on the ice powder, namely, a surfactant-containing solution layer without icing is formed on the part of the ice powder, when gas hydrate is generated in the surfactant solution, heat is released to melt adjacent ice powder particles, water generated by melting the ice powder particles continuously forms a new surfactant solution, and the formed new surfactant solution continuously forms gas hydrate with the gas. Through the circulation process of gas hydrate generation, ice powder melting and gas hydrate generation, the huge specific surface area of the ice powder and the good generation rate of the gas hydrate in the surfactant solution, the ice medium provided by the invention has the characteristics of high hydrate generation speed, high hydrate storage capacity and the like when being used for hydrate generation. In addition, when the using temperature of the ice medium is too low, a small amount of thermodynamic inhibitor or gas with relatively high temperature for generating hydrate can assist the surfactant to construct a local solution layer on the surface of the ice medium, so that the applicable temperature range of the ice medium for efficiently promoting gas hydrate generation can be expanded, namely, the thermodynamic inhibitor is added into the ice medium, the gas with relatively high using temperature for generating hydrate can generate hydrate at a lower temperature, the using temperature of the ice medium is expanded, and a rapid hydrate generation effect is obtained in a wider temperature range.

The ice medium for accelerating the generation of the gas hydrate is used for generating the gas hydrate under the condition that the temperature is less than 0 ℃, the generation speed of the hydrate is high, the gas storage amount of the hydrate is high, and the water conversion rate higher than 80% can be obtained in 5min, so that the defects of low speed, low gas storage amount, large heat release amount and the like existing in the process of generating the gas hydrate by adopting the prior art can be overcome; the preparation method of the ice medium is simple, low in energy consumption, low in cost and wide in temperature application range, and can be used in the fields of gas storage and transportation, gas separation and the like.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for the description of the embodiments will be briefly described, and it is obvious that the drawings in the following description are some embodiments of the present invention, and other drawings may be obtained according to the drawings without inventive effort for a person skilled in the art.

FIG. 1 is a graph showing the change in gas storage amount at the time of gas hydrate formation in example 1 of the present invention.

FIG. 2 is a graph showing the change in gas storage amount at the time of gas hydrate formation in example 2 of the present invention.

FIG. 3 is a graph showing the change in gas storage amount at the time of gas hydrate formation in example 3 of the present invention.

FIG. 4 is a graph showing the change in gas storage amount at the time of gas hydrate formation in example 4 of the present invention.

FIG. 5 is a graph showing the change in gas storage amount at the time of gas hydrate formation in example 5 of the present invention.

FIG. 6 is a graph showing the change in gas storage amount at the time of gas hydrate formation in example 6 of the present invention.

FIG. 7 is a graph showing the change in gas storage amount at the time of gas hydrate formation in example 7 of the present invention.

FIG. 8 is a graph showing the change in the amount of gas stored upon formation of gas hydrate in comparative example 1.

FIG. 9 is a graph showing the change in gas storage amount at the time of gas hydrate formation in comparative example 2.

FIG. 10 is a graph showing the change in gas storage amount at the time of gas hydrate formation in comparative example 3.

FIG. 11 is a graph showing the change in gas storage amount at the time of gas hydrate formation in comparative example 4.

FIG. 12 is a graph showing the change in the amount of gas stored upon formation of gas hydrate in comparative example 5.

FIG. 13 is a graph showing the change in gas storage amount at the time of gas hydrate formation in comparative example 6.

FIG. 14 is a graph showing the change in gas storage amount at the time of gas hydrate formation in comparative example 7.

Detailed Description

It should be noted that the term "comprising" in the description of the invention and the claims and any variations thereof in the above-described figures is intended to cover a non-exclusive inclusion, such as a process, method, system, article, or apparatus that comprises a list of steps or elements is not necessarily limited to those steps or elements that are expressly listed or inherent to such process, method, article, or apparatus.

The "range" disclosed herein is given in the form of a lower limit and an upper limit. There may be one or more lower limits and one or more upper limits, respectively. The given range is defined by selecting a lower limit and an upper limit. The selected lower and upper limits define the boundaries of the particular ranges. All ranges defined in this way are combinable, i.e. any lower limit can be combined with any upper limit to form a range. For example, ranges of 60-120 and 80-110 are listed for specific parameters, with the understanding that ranges of 60-110 and 80-120 are also contemplated. Furthermore, if the minimum range values listed are 1 and 2 and the maximum range values listed are 3,4 and 5, then the following ranges are all contemplated: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5.

In the present invention, unless otherwise indicated, the numerical range "a-b" represents a shorthand representation of any combination of real numbers between a and b, where a and b are both real numbers. For example, the numerical range "0-5" means that all real numbers between "0-5" have been listed throughout this disclosure, and "0-5" is only a shorthand representation of a combination of these values.

In the present invention, all the embodiments and preferred embodiments mentioned in the present invention may be combined with each other to form new technical solutions, unless otherwise specified.

In the present invention, all technical features mentioned in the present invention and preferred features may be combined with each other to form a new technical solution unless specifically stated otherwise.

In the present invention, all the steps mentioned herein may be performed sequentially or randomly, but are preferably performed sequentially, unless otherwise specified. For example, the method comprises steps (a) and (b), meaning that the method may comprise steps (a) and (b) performed sequentially, or may comprise steps (b) and (a) performed sequentially. For example, the method may further include step (c), which means that step (c) may be added to the method in any order, for example, the method may include steps (a), (b) and (c), may include steps (a), (c) and (b), may include steps (c), (a) and (b), and the like.

The present invention will be described in further detail with reference to the drawings and examples, in order to make the objects, technical solutions and advantages of the present invention more apparent. The following described embodiments are some, but not all, examples of the present invention and are merely illustrative of the present invention and should not be construed as limiting the scope of the invention. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention. The specific conditions are not noted in the examples and are carried out according to conventional conditions or conditions recommended by the manufacturer. The reagents or apparatus used were conventional products commercially available without the manufacturer's attention.

Example 1

The embodiment provides an ice medium for accelerating the generation of gas hydrate and a method for accelerating the generation of gas hydrate by using the ice medium, wherein the ice medium for accelerating the generation of gas hydrate is prepared by a preparation method comprising the following specific steps:

firstly preparing sodium dodecyl sulfate and water into an aqueous solution with the mass fraction of 600ppm, then placing the aqueous solution into an ice chest and freezing the aqueous solution into ice cubes, taking out the ice cubes, and smashing the ice cubes into ice powder with the particle size of less than 250 mu m by beating and grinding under the heat preservation of dry ice to obtain the ice medium, wherein the sodium dodecyl sulfate surfactant is uniformly distributed in the ice powder.

The method for accelerating the generation of gas hydrate comprises the following steps:

10g of the above-prepared ice powder was charged into a high-pressure reaction vessel having a capacity of 68 ml, frozen to-0.5℃and then the temperature of the ice powder was adjusted to-0.5℃by means of a temperature-controlling apparatus. The external temperature of the high-pressure reaction kettle is also maintained at-0.5 ℃. And (3) introducing methane precooled to-0.5 ℃ into the high-pressure reaction kettle, and immediately closing an air inlet valve of the high-pressure reaction kettle when the pressure in the high-pressure reaction kettle reaches 6MPa, and stopping introducing methane.

After the pressure in the high-pressure reaction kettle reaches 6MPa and the introduction of methane is stopped, the pressure in the high-pressure reaction kettle is rapidly reduced, namely methane hydrate is rapidly generated.

The methane hydrate gas storage amount change curve obtained through calculation is shown in figure 1. The methane pressure in the high-pressure reaction kettle reaches 6MPa at the time point of 0, and as can be seen from fig. 1, the methane hydrate gas storage amount reaches 176.9V/Vw after 5 minutes, namely, the methane under the standard condition of 176.9 volumes of water is stored in each volume of water, and the corresponding water conversion rate is 85.3%.

Example 2

10g of the above-prepared ice powder was charged into a high-pressure reaction vessel having a capacity of 68 ml, frozen to-1.4℃and then the temperature of the ice powder was adjusted to-1.4℃by means of a temperature-controlling apparatus. The external temperature of the high-pressure reaction kettle is also maintained at-1.4 ℃. And (3) introducing methane precooled to-1.4 ℃ into the high-pressure reaction kettle, and immediately closing an air inlet valve of the high-pressure reaction kettle when the pressure in the high-pressure reaction kettle reaches 6MPa, and stopping introducing methane.

After the pressure in the high-pressure reaction kettle reaches 6MPa and the introduction of methane is stopped, the pressure in the reaction kettle is rapidly reduced, namely methane hydrate is rapidly generated.

The methane hydrate gas storage amount change curve obtained through calculation is shown in figure 2. Taking the pressure of methane in the reaction kettle to reach 6MPa as a time 0 point, as can be seen from fig. 2, the gas storage amount of methane hydrate reaches 156.6V/Vw after 5 minutes, namely the methane under the standard condition of 156.6 volumes of water is stored in each volume of water, and the corresponding water conversion rate is 75.5%.

Example 3

a quantity of purified water is placed in an ice bin and frozen into ice. The ice cubes were removed and crushed into ice powder having a particle size of less than 250 μm by beating and grinding under dry ice with heat preservation. And (3) scattering sodium dodecyl benzene sulfonate accounting for 0.2% of the mass of the ice powder into the ice powder for 5 times, and continuously stirring the ice powder by using a medicine spoon precooled by dry ice in the mixing process, so that the ice powder and the sodium dodecyl benzene sulfonate powder are uniformly mixed, and the ice medium is obtained.

10g of the above-prepared ice powder mixed with sodium dodecylbenzenesulfonate, namely, ice medium was charged into a high-pressure reaction vessel having a volume of 68 ml and frozen to-0.5℃and then the temperature of the ice powder was adjusted to-0.5℃by means of a temperature control device. The external temperature of the high-pressure reaction kettle is maintained at-0.5 ℃. And (3) introducing methane precooled to-0.5 ℃ into the high-pressure reaction kettle, and immediately closing an air inlet valve of the high-pressure reaction kettle when the pressure in the reaction kettle reaches 6MPa, and stopping introducing methane.

The methane hydrate gas storage amount change curve obtained through calculation is shown in figure 3. The methane pressure in the high-pressure reaction kettle reaches 6MPa at the time point of 0, and as can be seen from fig. 3, the methane hydrate gas storage amount reaches 174.3V/Vw after 5 minutes, namely, 174.3 volumes of methane under standard conditions are stored in each volume of water, and the corresponding water conversion rate is 84.0%.

Example 4

Collecting snow which is not hardened in the open air environment, and mixing the snow with sodium dodecyl sulfate. Upon mixing, the snow was prevented from melting at room temperature by dry ice protection. Adding sodium dodecyl sulfate accounting for 0.2% of the mass of ice powder (snow particles) into snow for 5 times, and continuously stirring the snow particles by using a medicine spoon precooled by dry ice in the mixing process, so that the mixture is uniformly mixed with the sodium dodecyl sulfate powder to obtain the ice medium.

10g of the above-prepared snow particles uniformly mixed with sodium dodecyl sulfate, namely, the ice medium was charged into a high-pressure reaction kettle having a capacity of 68 ml, frozen to-0.5 deg.c, and then the temperature of the ice powder was adjusted to-0.5 deg.c by means of a temperature control device. The external temperature of the high-pressure reaction kettle is maintained at-0.5 ℃. Introducing methane pre-cooled to-0.5 ℃ into the high-pressure reaction kettle, immediately closing an air inlet valve of the high-pressure reaction kettle when the pressure in the high-pressure reaction kettle reaches 6MPa, and stopping introducing methane;

The methane hydrate gas storage amount change curve obtained through calculation is shown in fig. 4. The methane pressure in the high-pressure reaction kettle reaches 6MPa at the time point of 0, and as can be seen from fig. 4, the methane hydrate gas storage amount reaches 171.1V/Vw after 5 minutes, namely, the methane under the standard condition of 171.1 volumes of water is stored in each volume of water, and the corresponding water conversion rate is 85.5%.

Example 5

firstly, preparing sodium dodecyl sulfate, sodium chloride and water into an aqueous solution containing 600ppm of sodium dodecyl sulfate and 0.3wt% (mass fraction) of sodium chloride, then placing the aqueous solution into a freezer and freezing into ice cubes, taking out the ice cubes, and smashing the ice cubes into ice powder with the particle size smaller than 250 mu m by beating and grinding under the heat preservation of dry ice to obtain the ice medium, wherein the sodium dodecyl sulfate surfactant and the sodium chloride are uniformly distributed in the ice powder.

10g of the above-prepared ice powder was charged into a high-pressure reaction vessel having a capacity of 68 ml, frozen to-4.5℃and then the temperature of the ice powder was adjusted to-4.5℃by means of a temperature-controlling apparatus. The external temperature of the autoclave was also maintained at-4.5 ℃. And (3) introducing methane precooled to-4.5 ℃ into the high-pressure reaction kettle, and immediately closing an air inlet valve of the high-pressure reaction kettle when the pressure in the high-pressure reaction kettle reaches 6MPa, and stopping introducing methane. Wherein the mass concentration of the sodium chloride solution with the freezing point of-4.5 ℃ is 7.2wt%, namely, the mass fraction is C=7.2 wt%.

The methane hydrate gas storage amount change curve obtained through calculation is shown in fig. 5. As can be seen from FIG. 5, the methane hydrate gas storage amount reaches 167.9V/Vw after 5 minutes, namely, 167.9 volumes of methane under the standard condition is stored in each volume of water, and the corresponding water conversion rate is 80.9%.

Example 6

10g of the above-prepared ice powder was charged into a high-pressure reaction vessel having a capacity of 68 ml, frozen to-4.5℃and then the temperature of the ice powder was adjusted to-4.5℃by means of a temperature-controlling apparatus. The external temperature of the autoclave was also maintained at-4.5 ℃. And (3) introducing methane heated to 20 ℃ into the high-pressure reaction kettle, and immediately closing an air inlet valve of the high-pressure reaction kettle when the pressure in the high-pressure reaction kettle reaches 6MPa, and stopping introducing methane.

In this example, the molar amount of methane fed into the autoclave was about 166mmol, and the heat capacity of methane at 6MPa was 42.87 kJ/(kmol. K). The heat capacity reduction value of methane caused by temperature reduction before hydrate generation is small, so that the methane heat capacity change in the cooling process is ignored in the calculation process. Since the ice medium is almost entirely ice powder, 10g of ice medium having a temperature of-4.5℃and 166mmol of methane having a temperature of 20℃are subjected to free heat exchange, calculated as the heat capacity of ice of 2.1 kJ/(kg.K), and the overall temperature should be 1.7 ℃.

The heat supplied to the ice medium by the gas in this example melts 100% by weight of the ice powder, irrespective of the heat exchange between methane and the autoclave at-4.5 ℃. Even considering the heat exchange between methane and autoclave, it is sufficient to ensure that more than 0.25% by weight of the ice powder is melted, since the overall intake time is only 2 minutes.

The methane hydrate gas storage amount change curve obtained through calculation is shown in fig. 6. Taking the pressure of methane in the reaction kettle to reach 6MPa as a time 0 point, as can be seen from fig. 6, the gas storage amount of methane hydrate reaches 164.7V/Vw after 5 minutes, namely, the methane under the standard condition of 164.7 volumes of water is stored in each volume of water, and the corresponding water conversion rate is 79.4%.

Example 7

firstly, preparing sodium dodecyl sulfate, sodium chloride and water into an aqueous solution containing 600ppm of sodium dodecyl sulfate and 0.4wt% (mass fraction) of sodium chloride, then placing the aqueous solution into a freezer and freezing into ice cubes, taking out the ice cubes, and smashing the ice cubes into ice powder with the particle size smaller than 250 mu m by beating and grinding under the heat preservation of dry ice to obtain the ice medium, wherein the sodium dodecyl sulfate surfactant and the sodium chloride are uniformly distributed in the ice powder.

10g of the above-prepared ice powder was charged into a high-pressure reaction vessel having a capacity of 68 ml and frozen to-10℃and then the temperature of the ice powder was adjusted to-10℃by means of a temperature control device. The external temperature of the high-pressure reaction kettle is maintained at-10 ℃. And (3) introducing methane heated to 20 ℃ into the high-pressure reaction kettle, and immediately closing an air inlet valve of the high-pressure reaction kettle when the pressure in the high-pressure reaction kettle reaches 6MPa, and stopping introducing methane.

In the embodiment, the molar quantity of methane fed into the high-pressure reaction kettle is 166mmol, the heat capacity of methane at 6MPa is 42.87 kJ/(kmol.K), and the heat capacity reduction value of methane caused by temperature reduction before hydrate generation is small, so that the change of methane heat capacity in the cooling process is ignored in the calculation process. Since the ice medium is almost completely ice powder, and the heat capacity of ice is calculated as 2.1 kJ/(kg.K), 10g of ice medium with the temperature of-10 ℃ and 166mmol of methane with the temperature of 20 ℃ exchange heat freely, the whole temperature is finally-2.41 ℃, namely the ice powder cannot melt.

Although methane at 20℃does not melt the ice powder, 0.286g of solution, i.e. 0.246g of water, was kept in liquid form with a sodium chloride solution concentration of-10℃at a freezing point, i.e. a mass fraction of 14% by weight, i.e. 0.04g of sodium chloride in this example, the liquid water comprising 2.46% by mass of the total ice powder. In addition, methane at 20 ℃ can temporarily melt the surfaces of ice medium particles and also promote the formation of hydrates to a certain extent.

The methane hydrate gas storage amount change curve obtained through calculation is shown in fig. 7. Taking the pressure of methane in the reaction kettle to reach 6MPa as a time 0 point, as can be seen from fig. 7, the gas storage amount of methane hydrate reaches 162.6V/Vw after 5 minutes, namely, the methane under the standard condition of 162.6 volumes of water is stored in each volume of water, and the corresponding water conversion rate is 78.4%.

Comparative example 1

This comparative example provides a method of generating gas hydrate, which is different from example 3 in that after crushing ice cubes into ice powder having a particle size of less than 250 μm, 10g of crushed ice powder is directly charged into a high-pressure reaction vessel for methane hydrate generation without mixing sodium dodecylbenzenesulfonate therein.

After the pressure in the high-pressure reaction kettle reaches 6MPa and the introduction of methane is stopped, the pressure in the high-pressure reaction kettle rapidly starts to drop, but the drop rate is very slow, namely the generation rate of methane hydrate is very slow.

The methane hydrate gas storage amount change curve obtained through calculation is shown in fig. 8. The methane pressure in the high-pressure reaction kettle reaches 6MPa at the time 0 point, and as can be seen from FIG. 8, the methane hydrate gas storage capacity is only 23.4V/Vw after 5 minutes, namely, the methane under the standard condition of 23.4 volumes of water is stored in each volume of water, and the corresponding water conversion rate is 11.3%.

Comparative example 2

This comparative example provides a method for producing gas hydrate, which is different from example 1 in that the pre-cooling temperature of the autoclave, the external temperature of the autoclave, the temperature of the ice powder after charging into the autoclave, and the pre-cooling temperature of methane are all-2 ℃.

After the pressure in the high-pressure reaction kettle reaches 6MPa and the introduction of methane is stopped, the pressure in the high-pressure reaction kettle rapidly starts to drop, but the drop rate is slower, namely the generation rate of methane hydrate is slower.

The methane hydrate gas storage amount change curve obtained through calculation is shown in fig. 9. The methane pressure in the high-pressure reaction kettle reaches 6MPa at the time 0 point, and as can be seen from fig. 9, the methane hydrate gas storage capacity is only 104.4V/Vw after 5 minutes, namely, the methane under the standard condition of 104.4 volumes of water is stored in each volume of water, and the corresponding water conversion rate is 50.3%.

Comparative example 3

The present comparative example provides a method of generating gas hydrate, which is different from example 1 in that the pre-cooling temperature of the autoclave, the external temperature of the autoclave, the temperature of the ice powder charged into the autoclave, and the pre-cooling temperature of methane are all-4.5 ℃; the difference from example 5 is that the ice medium prepared in this comparative example does not contain the thermodynamic inhibitor sodium chloride; the main difference from example 6 is that the temperature of the gas for generating hydrate introduced in this comparative example was-4.5 c, and the temperature of the gas for generating hydrate introduced in example 6 was 20 c.

The methane hydrate gas storage amount change curve obtained through calculation is shown in fig. 10. The methane pressure in the high-pressure reaction kettle reaches 6MPa at the time point of 0, and as can be seen from fig. 10, the methane hydrate gas storage capacity is only 69.21V/Vw after 5 minutes, namely, 69.21 volumes of methane under the standard condition are stored in each volume of water, and the corresponding water conversion rate is 33.4%.

Comparative example 4

This comparative example provides a method for producing gas hydrate, which is different from example 1 in that the pre-cooling temperature of the autoclave, the external temperature of the autoclave, the temperature of the ice powder after charging into the autoclave, and the pre-cooling temperature of methane are all-6.5 ℃.

After the pressure in the high-pressure reaction kettle reaches 6MPa and the introduction of methane is stopped, the pressure in the reaction kettle rapidly starts to drop, but the drop rate is slower, namely the generation rate of methane hydrate is slower.

The methane hydrate gas storage amount change curve obtained through calculation is shown in fig. 11. The methane pressure in the high-pressure reaction kettle reaches 6MPa at the time 0 point, and as can be seen from FIG. 11, the methane hydrate gas storage capacity is only 46.7V/Vw after 5 minutes, namely, the methane under the standard condition of 46.7 volumes of water is stored in each volume of water, and the corresponding water conversion rate is 22.5%.

Comparative example 5

This comparative example provides a method of forming a gas hydrate, which is different from example 1 in that the sodium dodecyl sulfate aqueous solution is formulated so that the mass concentration of sodium dodecyl sulfate is 200ppm.

The methane hydrate gas storage amount change curve obtained through calculation is shown in fig. 12. The methane pressure in the high-pressure reaction kettle reaches 6MPa at the time 0 point, and as can be seen from FIG. 12, the methane hydrate gas storage capacity is only 76.9V/Vw after 5 minutes, namely, the methane under the standard condition of 76.9 volumes of water is stored in each volume of water, and the corresponding water conversion rate is 37.1%.

Comparative example 6

This comparative example provides a method of forming gas hydrate, which is different from example 1 in that the mass concentration of sodium dodecyl sulfate in the prepared aqueous solution of sodium dodecyl sulfate is 400ppm.

The methane hydrate gas storage amount change curve obtained through calculation is shown in fig. 13. With the pressure of methane in the high-pressure reaction kettleReaching 6MPa at time 0, it can be seen from FIG. 13 that methane hydrate gas storage amount is only 147.2V/V after 5 minutes _w I.e. 147.2 volumes of standard methane are stored per volume of water, with a corresponding water conversion of 70.9%.

Comparative example 7

This comparative example provides a method of forming gas hydrates which differs from example 6 only in that the temperature of use of the ice medium is-10 ℃, and differs from example 7 only in that no thermodynamic inhibitor is added during the preparation of the ice medium of this comparative example.

And (3) introducing methane heated to 20 ℃ into the high-pressure reaction kettle, and immediately closing an air inlet valve of the high-pressure reaction kettle when the pressure in the high-pressure reaction kettle reaches 6MPa, and stopping introducing methane.

After the pressure in the high-pressure reaction kettle reaches 6MPa and the introduction of methane is stopped, the pressure in the reaction kettle starts to drop, but the drop rate is slower, namely the generation rate of methane hydrate is slower.

In this comparative example, the molar amount of methane introduced into the autoclave was about 166mmol, the heat capacity of methane at 6MPa was 42.87 kJ/(kmol.K), and since the ice medium was almost entirely ice powder, 10g of ice medium at-10℃was free to exchange heat with 166mmol of methane at 20℃and the overall temperature was finally-2.41℃as calculated by the heat capacity of ice of 2.1 kJ/(kg.K), i.e., the ice powder was not melted.

Taken together, methane introduced at a temperature higher than 0 ℃ in this comparative example did not melt the ice medium. Even if the hot methane can partially melt the surface of the ice medium particles at the beginning, the aqueous solution formed by melting cannot exist stably because the temperature of the ice medium is too low and the temperature of the methane is not high enough.

The methane hydrate gas storage amount change curve obtained by calculation is shown in fig. 14. As can be seen from FIG. 14, the methane hydrate gas storage amount after 5 minutes is only 32.4V/V, taking the time 0 point when the methane pressure in the high-pressure reaction kettle reaches 6MPa _w I.e. 32.4 volumes of standard methane are stored per volume of water, with a corresponding water conversion of only 15.6%.

The experimental results of comparative examples 6 and 7 revealed that the ice medium of comparative example 7 had a lower use temperature of-10 c and the methane gas had a temperature of 20 c, compared to example 6, and the methane gas provided insufficient heat, resulting in a slower rate of hydrate formation of the ice medium. The experimental results of comparative example 7 and comparative example 7 show that in example 7, the addition of a thermodynamic inhibitor to an ice medium can accelerate gas hydrate formation in the case where hot methane is insufficient to create a stable aqueous solution in the ice medium as compared to comparative example 7.

Comparing the experimental data in fig. 1 to 14, it can be known that when the ice medium for accelerating the generation of gas hydrate provided by the embodiment of the invention is used for generating gas hydrate at the temperature of less than 0 ℃, the generation speed of the hydrate is high, the gas storage amount of the hydrate is high, and the water conversion rate (embodiment 4) of up to 85.5% and the gas storage amount (embodiment 1) of up to 176.9V/Vw can be obtained in 5min, namely, 176.9 volumes of methane is stored in each volume of water, thereby solving the defects of slow rate, low gas storage amount, large heat release and the like when the gas hydrate is generated by adopting the prior art; the preparation method of the ice medium is simple, low in energy consumption and low in cost, and can be used in the fields of gas storage and transportation, gas separation and the like.

The foregoing description of the embodiments of the invention is not intended to limit the scope of the invention, so that the substitution of equivalent elements or equivalent variations and modifications within the scope of the invention shall fall within the scope of the patent. In addition, the technical features and the technical features, the technical features and the technical invention can be freely combined for use.

Claims

1. An ice medium for accelerating gas hydrate formation, the ice medium comprising ice powder and surfactant uniformly distributed in the ice powder, or the ice medium comprising ice powder and surfactant uniformly distributed in the ice powder and thermodynamic inhibitor, wherein the surfactant accounts for more than 400ppm by mass of the ice medium, and the thermodynamic inhibitor accounts for less than C/5 by mass of the ice medium, wherein C is the mass fraction of an aqueous solution of thermodynamic inhibitor taking the use temperature of the ice medium as the freezing point, in wt%.

2. The ice media of claim 1, wherein the surfactant comprises one or a combination of sodium dodecyl sulfate, ammonium dodecyl sulfate, sodium dodecyl benzene sulfonate, dodecylbenzene sulfonic acid, sodium dodecyl sulfonate, and sodium laurate;

Preferably, the surfactant comprises one or a combination of several of sodium dodecyl sulfate, ammonium dodecyl sulfate, sodium dodecyl benzene sulfonate and sodium laurate.

3. The ice media of claim 1, wherein the thermodynamic inhibitor comprises salts and alcohols;

preferably, the thermodynamic inhibitor comprises one or a combination of several of sodium chloride, potassium chloride and ethylene glycol.

4. An ice medium according to any one of claims 1-3, wherein the ice powder has a particle size of less than 300 μm.

5. A method of preparing an ice medium for accelerating gas hydrate formation according to any one of claims 1 to 4, comprising:

or freezing pure water to form ice cubes, crushing the ice cubes into ice powder, and uniformly mixing a surfactant or a surfactant, a thermodynamic inhibitor and the ice powder to obtain the ice medium;

6. Use of an ice medium according to any one of claims 1-4 for accelerating gas hydrate formation.

7. A method for accelerating the formation of gas hydrates, wherein the method uses the ice medium for accelerating the formation of gas hydrates as claimed in any one of claims 1 to 4, comprising:

firstly, filling the ice medium into a reactor precooled to be less than 0 ℃, then, utilizing a temperature control device to adjust the temperature of the ice medium to be less than 0 ℃ for use, and then, introducing gas for generating hydrate into the reactor to generate gas hydrate.

8. The method according to claim 7, characterized in that it comprises in particular:

or when the use temperature of the ice medium is not higher than-1.5 ℃ and the gas temperature for hydrate formation is higher than 0 ℃, the ice medium comprises ice powder and surfactant uniformly distributed in the ice powder, or the ice medium comprises ice powder and surfactant and thermodynamic inhibitor uniformly distributed in the ice powder; filling the ice medium into a reactor precooled to the temperature not higher than-1.5 ℃, then adjusting the temperature of the ice medium to the use temperature not higher than-1.5 ℃ by utilizing a temperature control device, and then introducing gas for generating hydrate with the temperature higher than 0 ℃ into the reactor to generate gas hydrate;

Preferably, when the gas for hydrate formation having a temperature higher than 0 ℃ supplies heat to the ice medium sufficient to melt not less than 0.25wt% of the ice powder, and the melted solution is kept in a non-frozen state for 5 minutes after the gas pressure for hydrate formation reaches the hydrate formation pressure corresponding to the use temperature of the ice medium, the ice medium includes the ice powder and the surfactant uniformly distributed in the ice powder.

9. The method of claim 7 or 8, wherein the gas for hydrate formation comprises one or a combination of several of methane, ethane, propane, carbon dioxide and hydrogen sulfide.

10. The method according to claim 7 or 8, wherein if the gas for hydrate formation is a pure component gas, the gas pressure is maintained higher than the formation pressure of the hydrate of the gas at the use temperature of the ice medium; if the gas used for generating the hydrate is a mixed gas, the partial pressure of the gas component which is easy to form the hydrate in the mixed gas is kept higher than the generation pressure of the hydrate of the gas component which is easy to form the hydrate at the using temperature of the ice medium.