JP4022446B2 - Gas hydrate generation method and apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a gas hydrate method and apparatus for generating gas hydrate using a pseudo liquid layer on the surface of ice.
[0002]
[Prior art]
In general, gas hydrate is produced in a high-pressure and low-temperature atmosphere. For example, methane hydrate (hydrate) is formed based on the equilibrium line of FIG. That is, when the equilibrium temperature is 280 K (7 ° C.), the pressure reaches 40 atm.
[0003]
By the way, the gas (boil-off gas) evaporating from LNG (liquefied natural gas) stored in the LNG storage tank of the LNG receiving base is normal pressure. In order to generate gas hydrate using this boil-off gas, it is necessary to increase the pressure as can be seen from the above example.
[0004]
However, if the pressure of the boil-off gas is increased, there is no difference from the current situation where the pressure of the boil-off gas is increased by the compressor and sent to the city, and the significance of converting the boil-off gas into gas hydrate is lost.
[0005]
LNG is generally used as a form of transport of natural gas, but as a new form of transport, attention is focused on transporting natural gas into a solid substance such as pellets after hydrating the natural gas. . The reason is that it has the advantage that the gas hydrate (NGH) production energy is about half that of LNG.
[0006]
Hydration of boil-off gas at the LNG receiving terminal is the largest amount of gas as the target gas in the country, and its processing method can be flexibly adapted to gas supply and demand if it has low power cost and can be stored. There are advantages. For that purpose, energy saving is indispensable.
[0007]
On the other hand, when producing gas hydrate from ice at the solid-gas phase interface, it has been found that the smaller the initial particle size of ice and the larger the specific surface area, the higher the hydrate conversion rate.
[0008]
In general, the solubility of water and methane is very small, but the quasi-liquid layer on the surface of ice makes it possible to take in a large amount of methane by increasing with increasing specific surface area and also into the solid layer. Movement speed increases. If conditions (temperature and pressure) for generating gas hydrate are satisfied, gas hydrate is generated on the surface of ice. It is known that a pseudo liquid layer exists on the surface of ice at a temperature range of −0 ° C. to −20 ° C., and a pseudo liquid layer around −5 ° C. to −15 ° C. takes in a large amount of methane.
[0009]
By the way, although the experiment which produces | generates methane hydrate on the surface of ice is reported, this experiment is nothing but a thing using a pseudo liquid layer. For example, when producing methane hydrate at a temperature of −5 ° C. to −10 ° C., the equilibrium pressure is several tens of atmospheres. For example, if methane hydrate is produced at −80 ° C. or lower, The equilibrium point is normal pressure. When water is sprayed into methane gas having a temperature of −80 ° C. or lower, the water immediately forms an ice lump. However, when the temperature is −20 ° C. or lower, the diffusion of methane from the ice surface is extremely slow. In addition, it is industrially difficult to produce hydrate directly in an atmosphere of normal pressure.
[0010]
Therefore, as a result of diligent research, the present inventor first absorbed methane into the surface layer of fine ice blocks at normal pressure and in an environment of −15 ° C. or lower, and then in a different environment (−80 ° C. or lower). It was found that methane hydrate can be rapidly formed by charging to reach equilibrium conditions.
[0011]
[Problems to be Solved by the Invention]
The present invention has been made based on such knowledge, and a main object thereof is to provide a gas hydrate generation method and apparatus capable of efficiently generating gas hydrate from ice and boil-off gas. Is.
[0012]
[Means for Solving the Problems]
In order to achieve the above object, the gas hydrate production method of the present invention causes a gas below the freezing point to be ejected into the reaction tank, and water is sprayed into the gas to form fine ice particles. At the same time, gas is taken into the ice particles, and then the ice particles that have taken in the gas are introduced into the production tower, and the ice particles that have taken in the gas in the production tower are supercooled to produce a gas hydrate. It is characterized by.
[0013]
Moreover, the gas hydrate production | generation method of this invention is characterized by making an ice particle flow in a reaction tank and a production tank.
The gas hydrate production method of the present invention is characterized in that the atmosphere in the reaction tank is maintained at −0 ° C. to −20 ° C., and the atmosphere in the production tank is maintained at −80 ° C. or lower.
[0014]
On the other hand, the gas hydrate generator of the present invention ejects a gas below the freezing point from the porous bed into the reaction tank, and sprays water from the fluid jet nozzle into the gas to form fine ice particles. At the same time, the gas is taken into the ice particles, and then the ice particles that have taken in the gas are separated by a solid-gas separator and introduced into the production tower, and the ice particles that have taken in the gas in the production tower are supercooled. Thus, a gas hydrate is generated.
[0015]
The gas hydrate generator of the present invention is characterized in that a plurality of generation towers are installed.
Moreover, the gas hydrate production | generation apparatus of this invention is characterized by supercooling, circulating the supercooled refrigerant | coolant in a production | generation tower | column, and flowing the ice particle in a production | generation tower | column.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a system diagram of a gas hydrate generator according to the present invention.
As shown in FIG. 1, the gas hydrate generator 1 includes a vertical reaction tank 2, a vertical generator tower 3, a cyclone 4, a first heat exchanger 5, and a second heat exchanger 6. Yes.
[0017]
The boil-off gas a at normal pressure and at a very low temperature (about −150 ° C.) is supplied to the bottom of the reaction tank 2 via the first heat exchanger 5. This reaction tank 2 is provided with a porous bed 7 horizontally in the lower part thereof, and the above-described boil-off gas a is ejected from the numerous holes toward the upper side of the tank. The supply amount of the boil-off gas is adjusted so that the atmosphere in the reaction tank 2 maintains a range of −0 ° C. to −20 ° C.
[0018]
On the other hand, the reaction tank 2 is provided with a spray nozzle 8 at the top thereof, and sprays water b into the above-described boil-off gas a. The water b sprayed from the spray nozzle 8 comes into contact with the boil-off gas a and becomes fine ice particles c, and at the same time, the boil-off gas a is taken into the surface.
[0019]
The ice particles c taking in the boil-off gas a are blown up to the boil-off gas a ejected from countless holes of the perforated plate 7, flow in the reaction tank 2, and are introduced into the cyclone 4 through the pipe 9. The ice particles c introduced into the cyclone 4 are separated from the boil-off gas a and introduced into the production tower 3 through the pipe 10.
[0020]
The boil-off gas a discharged from the cyclone 4 is returned to the reaction tank 2 through the pipe 11. At that time, the flow of the boil-off gas a is promoted by the fan 12.
[0021]
The production tower 3 includes a circulation device 13, and the ice particles c introduced into the production tower 3 are fluidized by the refrigerant d flowing from the bottom to the top in the production tower 3. The refrigerant d, which is supercooled by the heat exchanger 6 of No. 2, is supercooled to −80 ° C. or lower, and gas hydrate e having high purity is continuously generated. The produced gas hydrate e is sent to the next process through a duct 14 connected to the bottom of the production tower 3.
[0022]
The circulation device 13 includes a communication pipe 15 that communicates the upper part and the lower part of the generation tower 3, a fan 16, and a second heat exchanger 6. The second heat exchanger 6 is configured to cool LNG (-162). The cooling medium d is supercooled by using (° C.) and the hydrate generation heat is removed.
[0023]
In the present invention, since the ice particles c are required to stay in the production tower 3 for a certain period of time, it is conceivable to install the production tower 3 in a plurality of stages, for example, two or more stages. In the case of FIG. 2, the production tower 3 has two stages, and the upper production tower 3 and the lower production tower 3 are communicated with each other through a communication pipe 17. In addition, the same code | symbol is attached | subjected to the same apparatus as the thing of embodiment of FIG. 1, and detailed description is abbreviate | omitted.
[0024]
In the above description, the case where a normal pressure boil-off gas and a refrigerant having a temperature of −80 ° C. or lower are applied has been described. However, if the temperature of the refrigerant is higher than −80 ° C., the gas hydrate is generated by increasing the pressure. Is possible.
[0025]
Further, although the case where the tank-type reaction tank and the tank-shaped production tower are applied has been described, it is also possible to apply a so-called tubular type apparatus using a tube instead of the tank.
[0026]
【The invention's effect】
As described above, the gas hydrate production method of the present invention causes a gas below the freezing point to be ejected into the reaction tank, and water is sprayed into the gas to form fine ice particles. The gas particles are taken into the ice particles, and then the ice particles into which the gas has been introduced are introduced into the production tower, and the ice particles that have taken in the gas in the production tower are supercooled to produce a gas hydrate. Gas hydrate can be efficiently generated under pressure. In addition, since the present invention generates gas hydrate from ice particles, dehydration of the generated gas hydrate becomes unnecessary, and the equipment cost and running cost can be reduced.
[0027]
On the other hand, the gas hydrate generator of the present invention ejects a gas below the freezing point from the porous bed into the reaction tank, and sprays water from the fluid jet nozzle into the gas to form fine ice particles. At the same time, the gas is taken into the ice particles, and then the ice particles that have taken in the gas are separated by a solid-gas separator and introduced into the production tower, and the ice particles that have taken in the gas in the production tower are supercooled. Since the gas hydrate is generated, the apparatus can be simplified and made compact in addition to the above effects.
[Brief description of the drawings]
FIG. 1 is a system diagram of a gas hydrate generator according to the present invention.
FIG. 2 is another system diagram of the gas hydrate generator according to the present invention.
FIG. 3 is three-phase data of methane hydrate.
[Explanation of symbols]
a low temperature gas b water c ice particles d gas hydrate 1 gas hydrate generator 2 reaction tank 3 generator tower 4 solid-gas separator 7 porous bed 8 fluid injection nozzle

Claims (6)

A gas below the freezing point is ejected into the reaction tank, and water is sprayed into the gas to form fine ice particles. At the same time, the gas is taken into the ice particles, and then the gas is taken in. A gas hydrate production method comprising introducing ice particles into a production tower, and supercooling the ice particles that have taken in the gas in the production tower to produce gas hydrate. The method for producing gas hydrate according to claim 1, wherein ice particles are flowed in the reaction tank and the production tank. The method for producing a gas hydrate according to claim 1 or 2, wherein the atmospheric temperature in the reaction tank is maintained at -0 ° C to -20 ° C, and the atmospheric temperature in the production tank is maintained at -80 ° C or lower. . A gas below the freezing point is ejected from the porous bed into the reaction tank, and water is sprayed into the gas from the fluid injection nozzle to form fine ice particles. After that, the ice particles that have taken in the gas are separated by a solid-gas separator and introduced into a production tower, and the ice particles that have taken in the gas in the production tower are supercooled to produce a gas hydrate. A gas hydrate generator. The gas hydrate generator according to claim 4, wherein a plurality of generation towers are installed. The gas hydrate generating apparatus according to claim 4 or 5, wherein a supercooled refrigerant is circulated in the generating tower and the ice particles in the generating tower are caused to flow while being supercooled.

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