RU2678159C2 - Storage tank for liquefied flammable gases - Google Patents

Abstract

FIELD: storage or distribution of gases or liquids.SUBSTANCE: invention relates to storage tanks for liquefied flammable gases. Full integrity spherical storage tank (80) comprising inner tank (82) of cryogenic steel, outer tank (83) of cryogenic steel, support structure (81), and outlet pipe (84) communicating with the interior of inner tank (82), and a burst disc in outer tank (83).EFFECT: prevention the release of flammable gas from a storage tank.15 cl, 8 dwg

Description

FIELD OF THE INVENTION

The present invention relates to tanks for storing liquefied combustible gases, such as liquefied natural gas (LNG, LNG - Liquified Natural Gas).

BACKGROUND

To prevent a catastrophic release of combustible gas from a tank for storing liquefied petroleum gas, such as a tank for storing liquefied natural gas, safety regulations have been established. Existing industrial safety standards for LNG include a safety classification for flat-bottom liquefied natural gas storage tanks as a single tank, a double tank, and a fully-sealed double-shell tank.

This classification does not apply to spherical type liquefied natural gas tanks. To enable comparison of industrial safety definitions for all types of tanks, further various storage tanks are classified according to their level of tightness:

A single level of tightness is the lowest classification level at which the catastrophic destruction of the internal capacity will lead to uncontrolled leakage of natural gas and the release of steam into the atmosphere.

With a double level of tightness, the destruction of the internal container will not lead to spillage of liquid, but such will lead to uncontrolled emission of natural gas vapors into the atmosphere.

The highest level is indicated as complete tightness and is designed to prevent any leakage of liquid and to ensure only a controlled release of vapor into the atmosphere.

For example, various configurations of tanks with a flat bottom are shown in figures 1-5. 6 and 7 depict configurations of spherical tanks.

Figure 1 shows a tank 10 with a flat bottom of a double level of tightness, containing a concrete base 11, an internal tank 12 of cryogenic steel, an external tank 13 of non-cryogenic steel and an additional tank bowl 14 of cryogenic steel. An exhaust pipe 15 is also shown.

FIG. 2 shows another configuration of a double-level flat bottom tank 20 containing a concrete base 21 and a dirt embankment 22, an internal cryogenic steel tank 23, an external non-cryogenic steel tank 24, and an exhaust pipe 25.

FIG. 3 shows a third configuration of a double-sealed flat bottom tank 30, comprising a concrete base and a containment structure 31 for a liquid, an internal tank 32 of cryogenic steel, an external tank 33 of non-cryogenic steel, and an exhaust pipe 34.

Figure 4 shows a fully sealed flat bottom tank 40 containing a concrete base 41, an inner cryogenic steel tank 42, an external cryogenic steel tank 43 and an exhaust pipe 44.

5 shows a second configuration of a fully sealed flat bottom tank 50 containing an internal cryogenic steel tank 52, a self-contained external non-cryogenic steel tank 53 supported by a concrete base and a two-shell structure 51 of a completely sealed type, and an exhaust pipe 54.

6 shows a spherical reservoir 60 of a single level of tightness, comprising a steel lower portion on a concrete base 61, an inner reservoir and a cryogenic steel support structure 62, an insulating layer 63 and an exhaust pipe 64.

7 shows a spherical tank 70 of a double level of tightness, containing a concrete base and a structure 71 for containing liquid, an inner tank and a supporting structure 72 of cryogenic steel, an insulating layer 73 and an exhaust pipe 74.

Currently there are no spherical tank configurations available that can be classified as fully sealed tanks; those. which provide a level of safety comparable to a fully-sealed two-shell tank with a flat bottom.

Typically, storage of liquefied petroleum gas in populated areas requires complete tightness. The reason is that single or double leakproof tanks do not provide sufficient protection against the effects of damage to the internal storage tank. In particular, these designs do not provide protection against the emission of vapors that will occur quickly in the event of a leak of liquefied gas in the area surrounding the tank or the secondary shell of the tank.

In addition, the catastrophic destruction of the primary tank can lead to the formation of a large, cold gas cloud, which poses a serious danger to the surrounding population due to the increased risk of fire or explosion. Despite the fact that a completely sealed storage tank can provide vapor to the atmosphere through pressure relief valves, such a discharge is carried out in a controlled manner and is much smaller in quantity.

For all of the foregoing reasons of the prior art, there remains a need to improve reservoirs for storing cryogenic liquid gases.

SUMMARY OF THE INVENTION

Based on the disadvantages and imperfections that are described above, and taking into account the prior art, which was discussed, the aim of the present invention is to improve storage tanks for cryogenic liquid gases.

This goal is achieved by means of a storage tank containing the features according to claim 1. Preferred embodiments and corresponding improvements of the present invention are disclosed in the dependent claims.

The present invention provides new configurations of fully sealed spherical tanks for storing cryogenic liquid gases. In particular, the present invention provides a completely sealed spherical type tank for storing liquefied combustible gases, such as for storing liquefied natural gas (LNG).

The completely sealed spherical type reservoir of the present invention is characterized in that it has both an inner reservoir and an outer reservoir, which are made of cryogenic steel. The completely sealed spherical storage tank of the present invention comprises a lower part, in particular made of steel, for example made of cryogenic steel, on a supporting structure, in particular made of steel, for example made of cryogenic steel, and an exhaust pipe communicating with the inner the space of the inner tank.

Advantages of the spherical reservoir of the present invention include the following:

Even if there is a leak from the inner tank, the outer tank will not fail due to fragility. In other words, due to the presence of an external reservoir made of cryogenic steel, the construction of the spherical reservoir of the present invention will remain operational even in the event of a catastrophic leak from the inner reservoir.

In addition, a bursting disc may be provided in the external reservoir to provide controlled release of vapors to a safe place in the event of a leak from the internal reservoir. No protective pit, embankment or embankment required.

In addition, due to the presence of an emergency shutdown valve (ESD) in the internal tank, it is possible to stop the system in the event of a leak in an adjacent pipe. This differs from conventional storage tank designs in which the emergency shut-off valve is located outside the tank.

Such an arrangement of the emergency shutdown valve is not a guarantee against a complete loss of reservoir stock in the event of a pipe rupture or leakage upstream of the emergency shutdown valve. As noted, due to the location of the emergency shutdown valve inside the tank, according to the present invention, the disadvantages of the design of the tanks of the prior art are overcome.

Other advantages of the present invention are that the spherical tanks meet the classification requirements as fully sealed storage tanks, and thus can be used in place of the double-shell storage tanks of a completely sealed type currently used in industry. With respect to the plurality of storage volumes, especially for storage of smaller volumes, spherical tanks are simpler, faster and less expensive to construct and install, and therefore provide advantages in terms of capital investment and construction costs over flat-bottom tanks.

In addition, the required abutment surface for the spherical tanks of the present invention is less than that for a flat-bottom tank or a standard spherical tank within a protective embankment. This is especially advantageous for storing liquefied natural gases at gas stations, for example, utility vehicles, since the highest level of safety is achieved with the smallest possible area, often surrounded by a high population density area.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the described embodiments of the present invention and, as already discussed above, there are several embodiments, as well as improvements to the idea of the present invention in a preferred manner. For this purpose, the present invention is described in more detail below; in particular, reference may be made to paragraphs depending on claim 1; further improvements, elements and advantages of the present invention are explained in more detail below with reference to a preferred embodiment by way of non-limiting example and to the accompanying drawings, taken at least in part in conjunction with the following description of embodiments in which:

Figure 1 is a schematic view for a first example of a tank with a flat bottom of a double level of tightness according to the prior art;

Figure 2 is a schematic view for a second example of a tank with a flat bottom of a double level of tightness according to the prior art;

Figure 3 is a schematic view for a third example of a tank with a flat bottom of a double level of tightness according to the prior art;

4 is a schematic view for a first example of a fully sealed flat bottom tank according to the prior art;

5 is a schematic view for a second example of a fully sealed flat bottom tank according to the prior art;

6 is a schematic view for an example of a spherical reservoir of a single level of tightness according to the prior art;

7 is a schematic view for an example of a spherical tank of a double level of tightness according to the prior art; and

Fig. 8 is a schematic view for an example of a fully sealed spherical tank according to the prior art.

DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION

Fig. 8 shows a fully sealed spherical-type storage tank 80, comprising a steel bottom for supporting the storage tank 80 on concrete supports 81, an internal cryogenic steel tank 82, an external cryogenic steel tank and support structure 83, and an exhaust pipe 84 in communication with the inner space of the inner tank 82; in particular, the supporting structure 81 can be integral with the external reservoir 83.

In addition, the spherical storage tank 80 includes an ESD (Emergency Shut Down) valve 85 located inside of the inner tank 82 and connected to the exhaust pipe 84. This emergency shutdown valve 85 ESD shuts off in the event of a leak or damage to an adjacent pipe.

A bursting disc is provided in the outer reservoir 83, said bursting disc providing a controlled release of vapor to a safe place in the event of a leak from the inner reservoir 82.

The storage tank 80 of FIG. 8 is provided for storing cryogenic liquid gases, in particular for storing liquefied combustible gases, for example for storing liquefied natural gases (LNG), such as for storing liquefied natural gases at gas stations for servicing freight vehicles .

It should be understood that other embodiments and modifications of the present invention will immediately become apparent to a person skilled in the art in light of the above description, and it is intended that such embodiments and changes also be included within the scope of the present invention as set forth in the appended claims.

LIST OF REFERENCE POSITIONS

80 - fully sealed spherical storage tank

81 - supporting structure

82 - inner tank

83 - external tank

84 - exhaust pipe

85 - emergency shutdown valve (ESD)

Claims (19)

1. A completely sealed spherical storage tank (80) containing: cryogenic steel inner tank (82); external tank (83) made of cryogenic steel; supporting structure (81); an exhaust pipe (84) in communication with the interior of the inner tank (82), and bursting disc in an external reservoir (83). 2. A completely sealed spherical storage tank according to claim 1, further comprising an emergency shut-off valve (85). 3. A completely sealed spherical storage tank according to claim 2, in which the emergency shut-off valve (85) is connected to the exhaust pipe (84). 4. A completely sealed spherical storage tank according to claim 2 or 3, in which the emergency shut-off valve (85) is located inside the internal tank (82). 5. A completely sealed spherical storage tank according to claim 2, in which the emergency shut-off valve (85) shuts off in the event of a leak or damage to an adjacent pipeline. 6. The completely sealed spherical storage tank according to claim 1, wherein the bursting disc provides controlled vapor release. 7. A completely sealed spherical storage tank according to claim 6, in which the steam is discharged to a safe location in case of leakage from the inner tank (82). 8. A completely sealed spherical storage tank according to claim 1, in which the supporting structure (81) is made of cryogenic steel. 9. A completely sealed spherical storage tank according to claim 1, in which the supporting structure (81) is made in one piece with the external tank (83). 10. A completely sealed spherical storage tank according to claim 1, configured to store cryogenic liquid gases. 11. The completely sealed spherical storage tank of claim 10, configured to store liquefied combustible gases. 12. A fully sealed spherical storage tank according to claim 11, configured to store liquefied natural gases (LNG). 13. Completely sealed spherical storage tank according to item 12, made with the possibility of storing LNG at gas stations. 14. Completely sealed spherical storage tank according to item 13, provided at gas stations for servicing vehicles.

Images