KR101034138B1 - Manufacturing method of the gas hydrate by using potential hydrate crystal - Google Patents

Abstract

The present invention relates to a method for producing gas hydrates using potential hydrate crystals. More specifically, the present invention provides a method for preparing a hydrate including: i) a first step of injecting a potential hydrate crystal of an aqueous solution containing a surfactant into the reactor, and ii) a potential hydrate crystal of the first step. It relates to a gas hydrate manufacturing method comprising a second step of pressurizing the injected reactor (gas).

Natural gas, hydrates, ice particles, slurries, porous materials, super absorbent polymers

Description

Method for manufacturing gas hydrate using potential hydrate crystals {MANUFACTURING METHOD OF THE GAS HYDRATE BY USING POTENTIAL HYDRATE CRYSTAL}

The present invention relates to a method for producing gas hydrates using potential hydrate crystals. More specifically, the present invention provides a method for preparing a hydrate including: i) a first step of injecting a potential hydrate crystal of an aqueous solution containing a surfactant into the reactor, and ii) a potential hydrate crystal of the first step. It relates to a gas hydrate manufacturing method comprising a second step of pressurizing the injected reactor (gas).

Natural gas is a fuel with cleanliness, stability, and convenience, and has been spotlighted as an alternative energy for solid fuels such as petroleum and coal, and its use in many fields such as home, commerce, transportation, and industry has been increasing. As an energy source that supplies a quarter, it forms the basis of the global energy industry along with solid fuels such as petroleum and coal.

When the natural gas is collected from the gas field and transported as it is, the volume is too large and there is a possibility of explosion, so to solve the problem, the natural gas is cooled to the liquefaction temperature to generate a liquefied natural gas (Liquefied Natural Gas) The method of storing and transporting in a dedicated tank installed in a transport ship etc. has been mainly used. Liquefied natural gas usually contains 600 times the volume of natural gas per unit volume.

However, methane gas, which is a major component of liquefied natural gas (LNG), requires very low temperatures of about -162 ° C for liquefaction. Therefore, it is very expensive not only for the production of liquefied natural gas but also for the manufacture of natural gas transportation equipment on the sea and on land. There is a problem.

Compressed gas is used as another natural gas storage and transportation method, but it is also difficult to manufacture a large container due to high storage pressure, which is technically difficult and expensive, and has a problem of safety due to high pressure explosion. .

Natural gas hydrates, on the other hand, are produced at relatively moderate pressures and temperatures while providing 170 times the volume of gas per unit volume. Once formed, the hydrates are preserved at -20 ° C and 1 atmosphere. These temperature and pressure conditions are much milder than those of liquefied natural gas and compressed gas.

In addition, natural gas hydrate is advantageous because it is unlikely to explode even when exposed to room temperature and atmospheric pressure, thereby ensuring sufficient time to replace the leakage and breakage of the system. That is, natural gas hydrates are safer and economical to store and transport than LNG or CNG.

Natural gas hydrate is a compound produced by the physical combination of gas and water at low temperature and high pressure, rather than chemical bonding, like dry ice. The calorific value of 1 ㎥ of gas hydrate is about 180㎥ It is similar to the calorific value of gas. Naturally, water and gas are buried in low temperature and high pressure undersea or frozen earth, which are easily decomposed into water and gas under dissociation conditions.

Natural gas hydrates are classified into type I, type II, type Η, etc. according to their molecular structure. Ice has a two-dimensional planar structure at low temperatures near 0 ° C, whereas water molecules form a three-dimensional cavity structure when natural gas hydrate is given the appropriate pressure (see Figure 1).

The size of a single pupil is about 1 nanometer and the unit cell size is about 2 nanometers, and natural gas enters the inside of the pupil. In other words, water molecules connected by hydrogen bonds become 'hosts' and gas molecules become 'guests'. The general formula of the gas hydrate is Gas (H ₂ O) _n where n is a hydration number, which has a value of about 5 to 8 depending on the size of the gas molecules. Van der Waals forces act between the nonpolar gas molecules and the water molecules.

A general method for producing natural gas hydrate is to generate natural gas hydrate by contacting water injected through a high pressure cooled natural gas supplied through a gas nozzle installed at the top of the reactor or a porous plate installed at the bottom of the reactor. Bubbling is the most common method, and since the entire reaction is exothermic, a cooling system is installed in the reactor or a system for lowering the temperature of the reactor from the outside to remove heat generated during the reaction.

However, this method has the disadvantage that the generated natural gas hydrate can cause plugging in the raw water or the natural gas injection nozzle, and when the spray plate is used, the mass transfer resistance is large due to the large diameter of the generated raw water particles. It is difficult to separate the generated natural gas hydrate and the unreacted water, and due to the low conversion rate, the amount of unreacted is high, which requires a lot of energy for the separation and reuse process.

In addition, the existing natural gas hydrate production method has a problem in industrialization due to long hydrate induction time and low hydrate crystal growth rate. Herein, the hydrate induction period may be defined as a period of time maintained in a meta-stable liquid state before the formation of solid gas hydrate crystal grains, and methane hydrate induction time is usually several days.

That is, for mass production, the problem of reducing the long hydrate induction time and the problem of low hydrate crystal growth rate must be solved. In order to reduce the hydrate induction time, the reaction area that can meet the temperature and pressure conditions and react must be wide. Conventional methods such as nozzle spraying, microbubbles, and agitation are used to increase the reaction area, but the conversion rate is limited and the manufacturing cost of the apparatus is high.

In addition, temperature and pressure conditions are important for the generation of hydrates, and a majority of the processes for hydrate generation are occupied by a cooling system for removing the heat of reaction generated during generation. Currently, a method of supplying cooled water to the inside and removing reaction heat through an external heat exchanger is used. However, in order to remove the heat of reaction generated when hydrates are generated inside, heat exchange must be performed through a high pressure reactor to manufacture a device. This difficult, high amount of hydrate to be produced makes mass production difficult because uniform heat exchange in the reactor is not possible.

In addition, since the hydrate is generated from the cooling surface of the heat exchanger, the heat conductivity is lowered by the adsorption of the heat exchanger surface and the hydrate after the formation of the hydrate (adhesion of ice in the refrigerating chamber), making the heat exchange in the reactor more difficult, and the separation is difficult. Will interfere.

Therefore, it overcomes the problems of the conventional gas hydrate manufacturing method as described above, there is no gas hydrate induction period and easy gas diffusion, while increasing the rate of gas hydrate crystal formation, while showing a high gas hydrate conversion rate, minimizing the process required for removing the reaction heat Therefore, the development of a new process for the gas hydrate manufacturing method that can reduce the production cost was urgently required in the utilization of natural gas energy.

The present invention facilitates gas diffusion during the production reaction and maximizes the contact area between water and gas, resulting in a high gas capture rate and shortening of the overall hydrate formation time, as well as high conversion and relatively low gas hydrate formation pressure. It is an object to provide a method for producing a hydrate.

In addition, the present invention does not require the latent heat according to the phase change (phase) compared to forming a gas hydrate directly in the aqueous solution, the total amount of heat generated in the reaction is reduced, the process for removing the reaction heat in the reactor is reduced to reduce the overall reaction efficiency It is an object of the present invention to provide a method for producing a gas hydrate that can increase the production cost by reducing the cooling process required to remove the reaction heat.

The object of the present invention is i) a first step of injecting a potential hydrate crystal of an aqueous solution containing a surfactant into the reactor, and ii) a potential hydrate crystal of the first step of injection It is achieved by providing a method for producing a gas hydrate comprising a second step of pressing the gas into the reactor.

It is also an object of the present invention to provide a method for producing a gas hydrate, characterized in that the potential hydrate crystal has a porous structure.

In addition, an object of the present invention is that a potential hydrate crystal having the porous structure is impregnated with an aqueous solution after i) impregnating an aqueous solution in the form of i) ice particles or ii) in the form of a slurry or iii) a porous material. Cooling the porous material, or iv) absorbing an aqueous solution containing a surfactant in the superabsorbent resin and then cooling the superabsorbent resin in which the aqueous solution is absorbed.

It is also an object of the present invention to provide a method for producing a gas hydrate which further comprises the step of cooling the reactor prior to injecting the potential hydrate crystals containing the surfactant into the reactor.

In addition, an object of the present invention is achieved by providing a method for producing a gas hydrate, characterized in that it further comprises the step of maintaining a constant pressure in the reactor through additional gas supply after injecting gas into the reactor.

The gas hydrate manufacturing method of the present invention already has a porous structure and does not require a separate hydrate induction time to convert to gas hydrate crystals. Potential hydrate crystals such as ice particles or powdered ice particles By using, it is possible to increase the diffusion rate of the reaction gas and maximize the contact area of water and gas to reduce the reaction time and maximize the reaction efficiency.

In addition, the gas hydrate manufacturing method of the present invention forms a gas hydrate from a potential hydrate crystal, and thus requires latent heat due to a phase change as compared to forming a gas hydrate directly in an aqueous solution. As a result, the total amount of reaction calorific value is reduced, resulting in a reduction in production cost and a process for removing reaction heat.

Gas hydrate manufacturing method using a potential hydrate crystal of the present invention comprises the steps of i) injecting a potential hydrate crystal (potential hydrate crystal) of the aqueous solution containing a surfactant into the reactor, and ii) the first The second step is to pressurize the gas into the reactor into which the potential hydrate crystal of the step is injected.

Here, gas hydrate is a low-molecular-weight gas and water at low temperature and high pressure exist as a solid state crystal like dry ice by physical bonding similar to structural entanglement rather than chemical bonding. Refers to a compound to be (see Figure 1).

In addition, since a potential hydrate crystal has a porous structure, it is converted into a gas hydrate crystal, and thus a precursor of a gas hydrate crystal without a separate hydrate induction time is required. It is called.

Potential hydrate crystals with a porous structure include 1) solid ice particles, or 2) insoluble forms of the surfactant-containing aqueous solution through a preliminary process of pre-cooling and pulverizing the aqueous solution containing the surfactant. Slurry form in the suspension state of the solid particles may be used.

In addition, instead of directly cooling and pulverizing the aqueous solution, 3) the aqueous solution is impregnated with the porous material and then cooled, or 4) the superabsorbent resin is absorbed and cooled, thereby eliminating the pre-crushing process. The aqueous solution can also be injected directly into the reactor.

At this time, the porous material or superabsorbent resin artificially separate the aqueous solution particles to maximize the contact area between the aqueous solution and the gas. In this case, all materials commercially available may be used as the porous material. Preferably, activated carbon, silica gel, or zeolite may be used. In addition, the superabsorbent polymer may be used all of the commercially available general resin, preferably polyacrylate, polyacrylamide (polyacryl amide), polyacryl acid, polymethacrylic acid, Polyethylene oxide, polyvinyl alcohol, and the like may be used.

When the reaction gas is injected into the reactor into which the above-described latent hydrate crystals are injected, the latent hydrate crystal forms gas hydrate directly with the injected gas (FIG. 2).

Due to the structural features of the potential hydrate crystals in porous form, gas diffusion in the potential hydrate crystals is facilitated, and the contact area between water and gas is maximized, resulting in high gas capture rates and shorter overall hydrate formation time. Conversion and relatively low gas hydrate formation pressure.

In addition, compared to forming a gas hydrate directly in an aqueous solution, no latent heat due to a phase change is required, which reduces the total amount of heat generated in the reaction, which reduces the apparatus and process for removing the reaction heat in the reactor. This will result in savings.

3 and 4 are schematic diagrams showing the calorific value to be removed from the outside, respectively, when forming a hydrate from an aqueous solution and when forming a hydrate in a crystal of a potential hydrate in an ice particle state, which is an embodiment of the present invention. As can be seen in Figures 3 and 4, when generating 1 kg of methane hydrate from an aqueous solution is 542.4 KJ / kg, the emission amount when generating 1 kg of methane hydrate from ice particles is absorbed at the phase change of 1 kg of ice particles from 542.4 KJ / kg That's 106.6 KJ / kg minus 435.8 KJ / kg of calories.

That is, since the aqueous solution containing the surfactant is in the form of ice particles and has already removed latent heat, the amount of heat to be removed in the reactor is reduced during the reaction, thus reducing the capacity and cooling time of the total cooler to remove the reaction heat in the reactor. Will be done.

The above mentioned potential hydrate crystals will comprise a surfactant, which can be used with all commonly used surfactants, but is preferably sodium dodecyl sulfate (SDS), diisooctyl sodium sulfo Succinate (diisooctyl sodium sulfosuccinate (DSS), sodium tetradecyl sulfate, sodium hexadecyl sulfate, sodium dodecylbenzene sulfonate, xylenesulfonate, sodium Sodium oleate, 4-n-decylbenzenesulfonate, sodium laurate, 4-dodecylbenzenesulfonic acid, dodecylamine hydro Dodecylamine hydrochloride, dodecyltrimethylammonium chloride, 4-n-octylbenzenesulfonate , Ethoxylated sulfonate, Decylbenzenesulfonate, Potassium oleate, n-decylbenzene sulfonate, Alkyltrimethylammonium bromide, C10 -C16 chains, Dodecyl amine, Tetradecyltrimethylammonium chloride, dodecyl polysaccharide glycoside, Cyclodextrins, Glycolipids, Lipoproteins Selected from lipoprotein-ipopeptides, phospholipides, para-toluene sulfonic acid, trisiloxane, tritone X-100 and mixtures thereof It is preferable.

The amount of the above-mentioned surfactant is sufficient in a small amount of about 0.5% of the total volume of the aqueous solution, and the concentration of the surfactant is preferably in the range of 50 ppm to 1000 ppm.

Meanwhile, the method may further include cooling the reactor before injecting the potential hydrate crystal containing the surfactant into the reactor. At this time, the cooling temperature of the reactor is preferably in the range of -10 ℃ to 10 ℃.

In addition, after the gas is injected into the reactor may further include the step of maintaining a constant pressure in the reactor through the additional gas supply. At this time, the pressure in the reactor is preferably in the range of 10 bar to 100 bar.

The gas injected into the reactor may be methane, ethane, propane, carbone dioxide, butane or mixtures thereof.

5 is a view of a gas hydrate manufacturing apparatus using ice particles of an embodiment of the present invention. The aqueous solution containing the surfactant is cooled and pulverized into ice particles, and then injected into the reactor (9), after which the reaction gas can be measured from the gas cylinder (1) through the pipe through the gas hydrate formation. It feeds through the nozzle 4 via the mass flowmeter 3.

At this time, the pressure is set through the gas regulator 2 to maintain a constant pressure in the reactor, and the coolant lines 13 and 14 are connected to the reactor in the cooler to which the temperature controller is attached to lower the temperature of the reactor.

Hereinafter, a gas hydrate manufacturing process using ice particles, which is an embodiment of the present invention, will be described.

≪ Example 1 >

Table 1 below shows methane gas hydrate formation experiments using ice particles. The reactor temperature was lowered through an external cooler near 0 ° C., and ice particles (300 ppm SDS) of aqueous solution were fed to the reactor. Methane gas was then fed to the reactor to maintain 50 bar to produce gas hydrate.

Reactor volume (L)
(Reactor Volume)
5
Methane Gas Consumption (Nm ³ )
(Methane Gas Consumption)
355
Liquid SDS Solution (L)
(Aqueous SDS Solution)
2.0
Initial reaction temperature / pressure
(Initial Reaction Temperature / Pressure)
0.1 ℃ / 50bar

Storage gas volume per luggage (v / v)
(Volumetric Gas Storage Per Hydrate)
165
Induction time for carbohydrate formation (min)
(Induction time for methane hydrates)
0

Methane Gas Sulfide Formation from Ice Particles

As can be seen in the above example, gas hydrates were immediately formed without induction time while injecting methane gas into the reactor to which all ice particles were injected.

The technical spirit of the present invention is not limited to the above specific embodiments and descriptions, and any person having ordinary knowledge in the technical field to which the present invention belongs without departing from the gist of the present invention claimed in the claims. Various modifications can be made from the technology, and it can be seen that such modifications fall within the protection scope of the present invention.

1 is a view for explaining the structure of a gas hydrate (gas hydrate).

2 is a conceptual diagram illustrating the concept of a gas hydrate manufacturing method using the potential hydrate crystal of the present invention.

Figure 3 is a schematic diagram showing the heat of reaction of the reactor using a conventional gas hydrate manufacturing method.

Figure 4 is a schematic diagram showing the heat of reaction of the reactor using an embodiment of the gas hydrate manufacturing method of the present invention.

5 is a detailed view of a gas hydrate manufacturing apparatus using an embodiment of the gas hydrate manufacturing method of the present invention.

[Drawing symbol]

1) gas tank 2) gas regulator

3) Mass Flow Meter (MFC) 4) Dual Nozzle

5) Aqueous tank 6) Pump

7) first thermocouple 8) second thermocouple

9) reactor 10) drain valve

11) pressure gauge 12) gas discharge line

13) Coolant in 14) Coolant out

Claims (17)

i) injecting a potential hydrate crystal of an aqueous solution containing a surfactant into the reactor; And ii) pressurizing a gas into the reactor into which the potential hydrate crystal of the first step is injected; Wherein the latent hydrate crystal has a porous structure, and the latent hydrate crystal having the porous structure is in the form of ice particles in an aqueous solution. delete delete i) injecting a potential hydrate crystal of an aqueous solution containing a surfactant into the reactor; And ii) pressurizing a gas into the reactor into which the potential hydrate crystal of the first step is injected; Wherein the latent hydrate crystal has a porous structure, and the latent hydrate crystal having the porous structure is in the form of a slurry of an aqueous solution. 5. The method of claim 1 or 4, wherein the potential hydrate crystal is made by cooling and pulverizing an aqueous solution. i) injecting a potential hydrate crystal of an aqueous solution containing a surfactant into the reactor; And ii) pressurizing a gas into the reactor into which the potential hydrate crystal of the first step is injected; Wherein the potential hydrate crystal has a porous structure, and the potential hydrate crystal having the porous structure impregnates the porous material with an aqueous solution, and then cools the porous material with the aqueous solution impregnated therein. Gas hydrate manufacturing method. 7. The method of claim 6, wherein the porous material is selected from active carbon, silica gel or zeolite. delete delete The method of claim 1, wherein the surfactant is sodium dodecyl sulfate (SDS), diisoctyl sodium sulfosuccinate (DSS), sodium tetradecyl sulfate (sodium hexa) Sodium hexadecyl sulfate, sodium dodecylbenzene sulfonate, xylenesulfonate, sodium oleate, 4-n-decylbenzenesulfonate , Sodium laurate, 4-dodecylbenzenesulfonic acid, dodecylamine hydrochloride, dodecyltrimethylammonium chloride, 4-n-octylbenzene Sulfonate (4-n- Octylbenzenesulfonate), Ethoxylated sulfonate, Decylbenzenesulfonate, Potassium oleate, n-decyl Zen sulfonate (n-Decylbenzene sulfonate), alkyltrimethylammonium bromide (C10-C16 chains), dodecyl amine, tetradecyltrimethylammonium chloride, dodecyl polysaccharide glycoside ( dodecyl polysaccharide glycoside, cyclodextrins, glycolipids, lipoprotein-lipopeptides, phospholipides, para-toluene sulfonic acid, trisilox A method for producing a gas hydrate, characterized in that it is selected from trisiloxane, triton X-100 and mixtures thereof. The method of claim 10, wherein the volume of the surfactant is within 0.5% of the total aqueous solution volume. 11. The method of claim 10, wherein the concentration of the surfactant is in the range of 50 to 1000 ppm gas hydrate manufacturing method. The method of claim 1, further comprising cooling the reactor prior to injecting a potential hydrate crystal with surfactant into the reactor. The method of claim 13, wherein the cooling temperature of the reactor is in the range of −10 ° C. to 10 ° C. 15. The method of claim 1, further comprising maintaining a constant pressure in the reactor through additional gas supply after injecting gas into the reactor. 16. The method of claim 15, wherein the pressure in the reactor is in the range of 10 bar to 100 bar. The method of claim 1, wherein the gas injected into the reactor is methane, ethane, propane, carbone dioxide, butane, or a mixture thereof.

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