JPH06294498A - Semi-underground liquefied fuel gas storage facility - Google Patents

Abstract

PURPOSE:To provide a safe semi-underground liquefied fuel gas storage facility puickly and surely diffusing the LNG overflowed on the ground surface via cracks of the tank cover of an LNG tank at the time of an earthquake to below the flashing concentration and preventing the occurrence of a fire and an explosion at a low cost. CONSTITUTION:Wire meshes 4 are doubly installed to surround the whole periphery of the tank cover 2 of an LNG tank 1 while the whole tank section is buried under the ground and the tank cover 2 at the upper end section is exposed on the ground, and multiple spray nozzles 5 spraying water sprays to the wire meshes 4 are radially installed on the outside of the wire meshes 4. When the leaked LNG passes through the wire meshes 4, its temperature quickly rises via the heat exchange with waterdrops, and it is lifted and diffused into the atmospheric air.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a semi-underground liquefied fuel gas storage facility.

[0002]

2. Description of the Related Art LNG (Liquified Natural Gas) is a natural gas containing methane as a main component, which is cooled and liquefied. At the time of liquefaction, all impurities such as sulfur and carbon dioxide in the gas are removed. Demand for gas, city gas, etc. is expanding, and almost all of this LNG depends on imports,
The landing storage facility has also been constructed in various parts of the country. This L
NG has an ignition temperature (5
40 ℃) is high, and the mixing ratio with air for combustion (5.
It can be said that the gas is relatively high (0 to 15.0%) and is relatively safe, but its storage facilities have taken various measures to prevent disasters caused by gas leaks such as earthquakes, and have implemented disaster prevention measures. One of the facilities is a semi-underground storage facility where the upper end of the LNG tank is exposed above ground and the entire tank is buried underground. It is considered that if the LNG tank is buried underground, most of the leakage of LNG to the ground can be prevented. Even if the LNG tank is cracked and liquid leaks due to a large earthquake that causes a ground crack, LNG will flow out to the ground. Not considered. However, it is not unthinkable that the liquid level of LNG will move violently due to the earthquake and the tank cover of the LNG tank will be destroyed. At that time, take measures to prevent the gasified LNG from leaking to the ground due to solar heat. is important.

Therefore, as shown in the vertical sectional view of FIG. 5 and the plan view of FIG. 6, an annular groove 03 is formed on the upper surface of the LNG tank 01 and surrounds the upper end of the tank and is divided into a plurality of sections in the circumferential direction. And each section and exhaust gas intake valve 0
Vertical common exhaust gas duct 0 whose lower end is connected via 4
6 and a semi-underground liquefied fuel gas storage facility having means for opening and closing the exhaust gas intake valve 04 according to the wind direction is proposed (Japanese Patent Application No. 4-59532). However, according to such a configuration, when LNG leaking to the ground due to damage of the tank cover 02 at the time of an earthquake is gasified by solar heat and overflows from the LNG tank 01, and flows along the surface of the earth,
LNG with a large specific gravity is stored in the annular groove 03, and blower 05
By sucking it up and releasing it from the exhaust gas duct 06 into the air, it is possible to reduce the LNG concentration to 5% or less and to eliminate the fear of a fire. When there is no wind, the LNG spreads over the entire annular groove 03, It is desirable to suck up from the direction, but normally the wind in the current wind direction overflows L
Since NG flows to the leeward side of the tank cover 02, the annular groove 03 is divided into a plurality of pieces in the circumferential direction, and a gas intake port is provided for each partition groove, and the intake valve 04 of this gas intake port is provided according to the wind direction.
Can be opened and closed.

However, since the semi-underground type storage facility digs a vertical hole to bury the LNG tank, it has a drawback that the manufacturing cost is higher than that of the above-ground type, and therefore the disaster prevention facility must be as low cost as possible. From this point of view, the above-mentioned disaster prevention equipment has a problem that it has an annular groove around the tank and a suction valve that opens and closes according to the wind direction, and there are several factors that increase the cost of the storage facility.

[0005]

SUMMARY OF THE INVENTION The present invention has been proposed in view of the above circumstances, and at low cost, LNG overflowing to the ground surface due to cracks in the tank cover of an LNG tank during an earthquake can be swiftly and reliably provided. It is an object of the present invention to provide a safe semi-underground liquefied fuel gas storage facility that diffuses below a flammable concentration and prevents the occurrence of fire and explosion.

[0006]

To this end, the present invention is directed to an LN in which the upper end is exposed above the ground and the entire tank is buried underground.
It is characterized in that it comprises a wire mesh which surrounds the entire upper end of the G tank and is installed in a single layer or more, and a plurality of spray nozzles which are installed outside the wire mesh so as to spray water spray to the wire mesh. To do.

[0007]

In the semi-underground liquefied fuel gas storage facility of the present invention, when LNG leaking to the ground due to damage to the tank cover during an earthquake occurs, it is gasified by solar heat, overflows from the LNG tank, and flows over the surface of the earth. In addition, the water spray sprayed from the spray nozzle onto the wire net becomes water droplets and hangs down the wire net, and when LNG passes through the wire net,
Due to heat exchange with water droplets, the temperature rises rapidly and rises to the atmosphere,
As a result, the leeward LNG concentration decreases. In addition, the water droplets on the wire mesh gradually cool and become ice, thereby gradually closing the mesh, so that the wire mesh acts as a dike, and as a result, LNG outflow is suppressed. Therefore, the LNG concentration can be further reduced.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to the drawings, an embodiment of the semi-underground liquefied fuel gas storage facility of the present invention will be described. FIG. 1 is a vertical sectional view of the storage facility, FIG. 2 is a plan view of the same as above, and FIG. Figure,
FIG. 4 is a vertical sectional view showing an operating state of the storage facility.

1 and 2, the LNG tank 1 is
This is a so-called semi-underground type in which the tank cover 2 at the upper end is exposed above the surface of the earth, and the entire tank part is buried underground. Inside, the LNG 3 is stored so that the liquid surface 3a is below the surface of the earth. A wire mesh 4 is installed double around the entire circumference of the tank cover 2 of the LNG tank 1, and a spray nozzle 5 for spraying water spray to the entire wire mesh 4 is provided outside each wire mesh 4.
Are radially arranged. The wire net 4 is shown in FIG.
As shown in, a plurality of wire meshes 4 with different mesh sizes
The a, 4b, and 4c are superposed and held by the wire mesh holder 4d, which has the function of making it difficult for water spray to pass through and increasing the thickness of ice generated by heat exchange with LNG.

In such a semi-underground liquefied fuel gas storage facility, the wire net 4 and the spray nozzle 5, which are provided as a risk preventing means against the leakage of LNG3 to the ground,
It is much cheaper than the conventional annular groove, exhaust gas intake valve, exhaust gas duct, etc. When the LNG leaked to the ground due to the damage of the tank cover 2 at the time of earthquake occurrence is gasified by solar heat and overflows from the LNG tank 1 and flows so as to crawl on the ground surface, as shown in FIG. The water spray 5a jetted from the wire mesh 4 into water droplets drops into the wire mesh 4 as it drops, and when the leaked LNG 3b passes through the wire mesh 4, the temperature rises rapidly due to heat exchange with the water droplets and the air is released. As a result, the leeward LNG concentration falls below the flammability concentration. The water droplets on the wire net 4 are cooled and ice 5
By gradually becoming b, the mesh of the wire mesh 4 is gradually closed, and thus the wire mesh 4 acts as a dike, and as a result, the leakage of the leaked LNG 3b to the leeward side is suppressed, so that the wire mesh 4 can be swiftly and more quickly. The LNG concentration can be surely lowered.

[0011]

In summary, according to the present invention, the wire mesh is installed in a single layer or more so as to surround the entire upper end of the LNG tank in which the upper end is exposed above the ground and the entire tank is buried underground. By having a plurality of spray nozzles installed to spray water spray on the same wire mesh on the outside,
A safe semi-underground liquefied fuel gas storage facility that is low-cost and that quickly and reliably diffuses LNG that overflows to the surface due to cracks in the tank cover of the LNG tank at the time of an earthquake to below the flammable concentration to prevent fires and explosions. Therefore, the present invention is extremely useful in industry.

[Brief description of drawings]

FIG. 1 is a vertical sectional view of an embodiment of a semi-underground liquefied fuel gas storage facility of the present invention.

FIG. 2 is a plan view of the above.

FIG. 3 is a vertical sectional view of a wire mesh.

FIG. 4 is a vertical sectional view showing an operating state of the storage facility.

FIG. 5 is a vertical cross-sectional view of a conventional semi-underground liquefied fuel gas storage facility.

FIG. 6 is a plan view of the above.

[Explanation of symbols]

 1 LNG tank 2 Tank cover 3 LNG 3a Liquid level 4, 4a, 4b, 4c Wire mesh 5 Spray nozzle 5a Water spray 5b Ice

Claims (1)

[Claims] 1. A wire net which surrounds the entire upper end of an LNG tank in which the upper end is exposed above the ground and the entire tank is buried underground, and a single or more wire mesh is installed, and water is sprayed onto the wire mesh outside the wire mesh. A semi-underground liquefied fuel gas storage facility, characterized by comprising a plurality of spray nozzles installed so as to inject the fuel.