KR20100133697A - Lng storage tank - Google Patents

Abstract

PURPOSE: An LNG storage tank is provided to increase the loading capacity of the LNG storage tank by the reduction in the length of a chamfer. CONSTITUTION: An LNG storage tank comprises a coffer dam. The coffer dam partitions the internal space of the floating marine structure in a longitudinal direction to reduce sloshing influence. The LNG storage tanks are arranged in two rows inside the floating marine structure. The size of the chamfer is reduced. The support structure, supporting a sealing member and an insulating member, is formed of trihedrons(121,123).

Description

ＬＮＧ Storage Tank {LNG STORAGE TANK}

The present invention relates to an LNG storage tank, and more particularly, to an LNG storage tank in which a support structure is simplified while reducing the length of a chamfer in a floating offshore structure.

Natural gas is transported in a gaseous state through onshore or offshore gas piping, or to a distant consumer while stored in an LNG carrier in the form of liquefied liquefied natural gas (LNG). Liquefied natural gas is obtained by cooling natural gas to cryogenic temperature (approximately -163 ℃), and its volume is reduced to about 1/600 than natural gas in gas state, so it is very suitable for long distance transportation through sea.

LNG carriers for loading LNG into the sea and loading and unloading LNG to land requirements include LNG storage tanks (commonly referred to as cargo holds) that can withstand the cryogenic temperatures of liquefied natural gas. LNG storage tanks installed inside LNG carriers can be classified into independent type and membrane type depending on whether the load directly affects the insulation.

Independent tank type storage tanks include SPB type or Moss type storage tanks. These types of storage tanks use a large amount of non-ferrous metal as the main material, which greatly increases the manufacturing cost of the storage tanks. Currently, LNG storage tanks are the most frequently used membrane storage tanks. Membrane storage tanks are relatively inexpensive and have been proven in LNG storage tanks for a long time without causing any safety problems. .

Membrane type storage tanks are further divided into GTT NO 96 type and Mark III type, which are described in US Pat. Nos. 5,269,247, 5,501,359, and the like.

The GTT NO 96 type storage tank includes a primary sealing wall and a secondary sealing wall made of Invar steel (36% Ni) having a thickness of 0.5 to 0.7 mm, a plywood box and a perlite. The primary heat insulation wall and the secondary heat insulation wall which consist of) are alternately laminated on the inner surface of a ship body.

In the case of the GTT NO 96 type, the primary sealing wall and the secondary sealing wall have almost the same degree of liquid tightness and strength, so that when the leakage of the primary sealing wall occurs, the secondary sealing wall can support the cargo safely for a considerable period of time. . Also, the sealing wall of GTT NO 96 type is easy to weld than the Mark III type membrane because the membrane is straight type, so the automation rate is high, but the overall welding length is longer than Mark III type. In addition, in the case of GTT NO 96, a double couple is used to support an insulation box (that is, an insulation wall).

Meanwhile, the Mark III type storage tank includes a primary sealing wall made of stainless steel membrane having a thickness of 1.2 mm and a secondary sealing wall made of a triplex, and a polyurethane foam. The primary heat insulating wall and the secondary heat insulating wall made of the back and the like are alternately provided on the inner surface of the hull.

In the case of Mark III type, the sealing wall has corrugated wrinkles, and shrinkage by the cryogenic LNG is absorbed by the corrugated wrinkles so that a large stress is not generated in the membrane. Mark Ⅲ type heat dissipation system is not easy to reinforce due to its internal structure, and its feature of preventing LNG leakage is weaker than that of GTT NO 96 type secondary sealing wall due to the characteristics of secondary sealing wall.

The liquefied natural gas storage tank of the membrane type described above is more vulnerable to the sloshing problem because the rigidity is weak in structural characteristics compared to the stand-alone type. Sloshing refers to a phenomenon in which a liquid substance, ie, LNG, flows in a storage tank when a vessel moves in various sea conditions, and the wall surface of the storage tank is severely impacted by sloshing.

In particular, as the demand for floating offshore structures such as LNG Floating, Production, Storage and Offloading (FPSO) or LNG Floating Storage and Regasification Unit (FSRU) has been increasing recently, LNG storage tanks installed in such floating offshore structures Even the sloshing problem was required.

LNG FPSOs are floating offshore structures that are used to produce and liquefy natural gas directly from the sea and store it in LNG storage tanks and, if necessary, to transport LNG stored in the LNG storage tanks to LNG carriers. In addition, LNG FSRU is a floating offshore structure that stores LNG unloaded from LNG carriers in the LNG storage tank in the sea far from the land, and then vaporizes LNG as needed to supply land demand.

Since this sloshing phenomenon inevitably occurs during the operation of the ship and while the floating offshore structure is at sea, it is necessary to design the storage tank structure to have sufficient strength to withstand the impact force caused by the sloshing.

1 is a schematic cross-sectional view of a floating offshore structure having a conventional single row LNG storage tank. The floating offshore structure 1 of FIG. 1 includes an upper sloped at an angle of 45 degrees to the upper and lower sides of the LNG storage tank 10 to reduce the sloshing impact force of the LNG, in particular, the sloshing impact force in the left and right directions; An example of an LNG storage tank 10 with lower chamfers 11, 12 is shown.

Thus, by forming the chamfer (11, 12) on the upper and lower portion of the storage tank 10, it is possible to solve the problem due to the sloshing phenomenon to some extent.

On the other hand, the sloshing impact force increases as the width of the LNG storage tank 10 increases, but conventionally, the LNG storage tank 10 is arranged in one row along the longitudinal direction of the hull so that the width of the LNG storage tank 10 is increased. Since the direction width is large, the sloshing impact force becomes large, and accordingly, the sizes of the chamfers 11 and 12 have to be large. In a conventional single row LNG storage tank, the vertical length of the chamfer had to be 2.5 m or more.

However, when the size of the chamfer is increased, the loading capacity of the LNG storage tank is reduced by that much, there is a problem that the economic efficiency is lowered.

In particular, in the case where the LNG storage tank is a GTT NO 96 type storage tank, a support structure for supporting the sealing member and the heat insulating member constituting the storage tank at a portion where the front and rear walls of the LNG storage tank meet the upper and lower walls, the side walls, and the chamfer. Trihedron and Invar Tube are used.

Triheadron is about 3t thick and has high material cost instead of stiffness, while Invar tube is about 1.5t thick and has low material cost instead of stiffness. Triheadrons are installed at the corners, and when the gaps between the corners are large, Invar tubes are installed between the corners. In the case of a conventional single row LNG storage tank, the vertical length of the chamfer is 2.5 m or more. And the chamfer is inclined at an angle of 45 degrees, so that the mounting length of the chamfer is considerably larger than 3.5 m, i.e. the gap between the edges comprising the chamfer, more particularly the edge between the upper and lower walls and the chamfer. Since the sidewalls have a large gap between the edges forming the chamfers, in the conventional LNG storage tanks arranged in a single row, the edges and sidewalls forming the upper and lower walls with the chamfers are chamfered. In forming the edge to be fitted between the tube-environment.

 FIG. 2 is a perspective view schematically illustrating an inner surface of a portion where the front and rear walls meet the upper and lower walls, the side walls, and the chamfer in the case of a conventional LNG storage tank arranged in a single row. In FIG. 2, the front and rear barriers 13 are actually front or rear walls, and thus the front and rear walls have the same configuration. In addition, the upper and lower walls 14 in FIG. 2 is actually an upper wall or a lower wall, but since the configuration of the upper wall and the lower wall is the same, it will be referred to as an upper and lower wall in the present specification.

As shown in FIG. 2, the triheadron is bent at an angle of 135 degrees at the upper and lower edges of the upper and lower walls 14 and the chamfer 12 to face the front and rear walls 13 and the chamfer. The upper and lower triheadrons 21 extending in both directions over the 12 and the side wall 16 and the side wall 16 is folded at an angle of 135 degrees at the side edges of the chamfer 12 to face the front and rear walls 13 and A lateral triheadron 23 extending in both directions across the chamfer 12.

An invar tube 25 is connected between the upper and lower triheadrons 21 and the side triheadrons 23. The triheadrons 21 and 23 and the invar tube 25 are connected to each other by a connector (not shown). The length of one side of the triheadron is preferably 0.67-0.77 m in consideration of the strength and the material cost. Therefore, the length of the one side of the triheadron is 0.67-0.77 m.

The present invention for solving these problems, while reducing the length of the chamfer in the floating offshore structure and at the same time supporting the sealing wall and the insulating wall constituting the storage tank between the edges containing the reduced chamfer It is an object of the present invention to provide an LNG storage tank with a simplified support structure.

According to an aspect of the present invention for achieving the above object, is a membrane-type LNG storage tank that can be installed in the floating offshore structure to store LNG, the storage tank is the floating tank to reduce the effects of sloshing phenomenon Comprising a cofferdam for dividing the internal space of the offshore structure in the longitudinal direction disposed in two rows in the floating offshore structure, forming a chamfer on the upper and lower sides of the storage tank arranged in two rows, including the chamfer The membrane-type LNG storage tank is provided by reducing the size of the chamfer so that the support structure for supporting the sealing member and the heat insulating member constituting the storage tank between the edges can be configured as a triheadron without an invar tube. do.

The corners including the chamfers may be upper and lower edges of the upper and lower walls and the side edges of the storage tank and the sidewalls of the chamfer. .

Preferably, the chamfer is inclined at an angle of 45 degrees, the vertical length of the chamfer is 1.01-1.11 m, and the mounting length of the chamfer is 1.42-1.56 m.

The triheadron is bent at an angle of 135 degrees at the upper and lower edges and the side edges, and the mounting length of one side of the triheadron is 0.71-0.78 m.

The membrane LNG storage tank is preferably a GTT NO 96 storage tank.

The triheadron includes upper and lower triheadrons extending in both directions between the upper and lower walls and the chamfers at the upper and lower edges of the upper and lower walls and the chamfers, and at the side edges of the sidewalls forming the chamfers. And a side triheadron extending in both directions across the sidewall and the chamfer while facing the front and rear walls, wherein the upper and lower triheadrons and the side triheadrons are connected to each other by a connector.

The floating offshore structure is any one selected from the LNG FPSO, LNG FSRU, LNG transport ship and LNG RV, which is used in the floating state at the flow where the flow occurs while having a storage tank for storing the liquid cargo loaded in the cryogenic state It may be.

In addition, according to another aspect of the present invention for achieving the above object, is a membrane type LNG storage tank that can be installed in the floating offshore structure to store LNG, while reducing the length of the chamfer of the storage tank at the same time Membrane type LNG storage tank is provided, characterized in that the support structure for supporting the sealing wall and the heat insulating wall constituting the storage tank between the edge including the chamfer is reduced by triheadron without the invar tube.

According to the LNG storage tank of the present invention as described above, the support for supporting the sealing wall and the insulating wall constituting the storage tank between the edges including the chamfer reduced in length while reducing the length of the chamfer Since the structure is composed of a triheadron without an inva tube, as the length of the chamfer is reduced, the loading capacity of the LNG storage tank is increased, thereby improving economic efficiency, and also simplifying the installation of the support structure at the chamfer portion. It works.

Hereinafter, an LNG storage tank for storing LNG in a floating offshore structure according to a preferred embodiment of the present invention will be described in detail with reference to the drawings.

In the present specification, a floating offshore structure is a concept including both a structure and a vessel used while floating in an ocean where a flow occurs while having a storage tank for storing a liquid cargo loaded at a cryogenic state such as LNG. For example, it includes both LNG carriers and LNG Regasification Vessels (RVs) as well as offshore structures such as LNG Floating, Production, Storage and Offloading (FPSO) or LNG Floating Storage and Regasification Units (FSRU).

3 is a schematic cross-sectional view of a floating offshore structure having two LNG storage tanks arranged in accordance with an embodiment of the present invention.

As shown in FIG. 3, the LNG storage tank 110 of the floating offshore structure 100 according to the embodiment of the present invention is a membrane-type LNG storage tank of the GTT NO 96 type, and the LNG contained therein. In order to reduce the impact due to the sloshing phenomenon includes a longitudinal cofferdam 115 is installed to divide the inner space of the floating offshore structure along the longitudinal direction.

The longitudinal cofferdam 115 allows the storage tank 110 to have two complete storage spaces without discontinuities in the insulation and sealing walls. In other words, according to the present invention, instead of dividing one storage tank into two spaces, the inner space of the floating offshore structure is divided along the longitudinal direction, and a separate storage tank is installed in each of these spaces. Can be.

In the present invention, the cofferdam is a lattice-shaped structure in which void spaces are provided between longitudinal cofferdam partition walls (bulkheads), and the inner space of the floating offshore structure is vertically and horizontally divided into a membrane in each compartment. It is a structure to install the type storage tank.

By arranging the storage tanks 110 in two rows, the impact force due to sloshing applied to the storage tanks may be drastically reduced. Considering the numerical results, it can be understood that the sloshing impact force is greatly reduced for two reasons. Firstly, the impact force due to sloshing is reduced by reducing the amount of cargo, that is, LNG, stored in one storage tank. Secondly, as the width of the storage tank is reduced by more than half, the motion intrinsic period of the liquid cargo, that is, LNG, is far from the intrinsic period of the floating offshore structure, thereby reducing the size of the liquid cargo.

In addition, in order to reduce the sloshing impact force of the LNG, particularly the sloshing impact force in the left and right directions, upper and lower chamfers 111 and 112 inclined at an angle of 45 degrees are formed on the upper and lower sides of the LNG storage tank 110. In the present invention, since the impact force due to the sloshing applied to the storage tank is sharply reduced by arranging the storage tanks 110 in two rows, the size of the chamfers 111 and 112 is not increased.

Accordingly, in the embodiment of the present invention, the chamfers 111 and 112 are formed to be inclined at an angle of 45 degrees, but the vertical length of the chamfers 111 and 112 is preferably reduced to 1.01-1.11 m, more preferably 1.06 m. I was. If the vertical lengths of the chamfers 111 and 112 are 1.01-1.11 m, the mounting length of the chamfers is 1.42-1.56 m, and the vertical lengths of the chamfers 111 and 112 are 1.06 m. The length is 1.49 m.

In the case where the LNG storage tank is a storage tank of GTT NO 96 type, generally, as a support structure for supporting the sealing member and the heat insulating member that constitute the storage tank, at the site where the front and rear walls of the LNG storage tank meet the upper and lower walls, the side walls, and the chamfer. Trihedron and Invar Tube are used.

4 is a perspective view schematically showing an inner surface of a portion where the front and rear walls meet the upper and lower walls, the side walls, and the chamfer in the case of the LNG storage tanks arranged in two rows according to an embodiment of the present invention. In FIG. 4, the front and rear barriers 113 are actually front or rear walls, and thus the front and rear walls have the same configuration. In addition, in FIG. 4, the upper and lower part walls 114 are actually upper or lower walls, but since the upper and lower walls have the same configuration, the upper and lower part walls 114 will be referred to as upper and lower part walls in the present specification.

As shown in FIG. 4, the triheadron is bent at an angle of 135 degrees at the upper and lower edges of the upper and lower wall 114, which forms the chamfer 112, so that the upper and lower wall 114 and the chamfer (the upper and lower walls 114) are opposed to the front and rear walls 113. The upper and lower triheadrons 121 extending in both directions over the 112 and the side wall 116 are bent at an angle of 135 degrees at the side edges of the chamfer 112 to face the front and rear walls 113 and the chamfer 113 and the chamfer. Side triheadron 123 extending in both directions over 112.

It is preferable that the length of the broken head is 0.67-0.77 m in consideration of the strength and the material cost, and therefore, the length of the broken head of the trihead is 0.67-0.77 m. According to an example, the mounting length of the chamfer is reduced from 1.42-1.56 m above 3.5 m, so that the front and rear walls of the storage tank, in particular, between the upper and lower walls, the side walls and the chamfer between the edges containing the chamfers. The support structure for supporting the sealing member and the heat insulating member between the corners of the upper and lower walls forming the chamfer and the sidewalls forming the chamfer can be configured as a triheadron without an inva tube.

That is, as shown in Fig. 4, the upper and lower triheadron 121 or the side triheadron 123 has a mounting length of 0.71-0.78 m, and the upper and lower triheadrons 121 and the side triheadrons 123 The loans 23 are connected to each other by a connector (not shown).

As described above, the LNG storage tank according to the present invention has been described with reference to the illustrated drawings, but the present invention is not limited to the embodiments and drawings described above, and in the technical field to which the present invention belongs within the claims. Of course, various modifications and variations can be made by those skilled in the art.

1 is a schematic cross-sectional view of a conventional LNG storage tank arranged in a row.

FIG. 2 is a perspective view schematically illustrating an inner surface of a portion where the front and rear walls meet the upper and lower walls, the side walls, and the chamfer in the case of a conventional LNG storage tank arranged in a single row.

3 is a schematic cross-sectional view of an LNG storage tank arranged in two rows according to an embodiment of the present invention.

4 is a perspective view schematically showing an inner surface of a portion where the front and rear walls meet the upper and lower walls, the side walls, and the chamfer in the case of the LNG storage tanks arranged in two rows according to an embodiment of the present invention.

Claims (8)

Membrane type LNG storage tank installed in the floating offshore structure to store LNG, The storage tank is arranged in two rows in the floating offshore structure, including a cofferdam for longitudinally dividing the internal space of the floating offshore structure to reduce the effect of sloshing phenomenon, A chamfer is formed on the upper and lower sides of the storage tanks arranged in two rows, and the support structure for supporting the sealing member and the heat insulating member constituting the storage tank between the edges of the chamfer without an inva tube. Membrane type LNG storage tank, characterized in that to reduce the size of the chamfer to be configured as. The method according to claim 1, The corners including the chamfers may include upper and lower edges of the upper and lower walls and the side edges of the storage tank and the sidewalls of the chamfer. Membrane type LNG storage tank. The method according to claim 2, The chamfer is inclined at an angle of 45 degrees, The vertical length of the chamfer is 1.01-1.11 m, the mounting length of the chamfer membrane type LNG storage tank, characterized in that 1.42-1.56 m. The method according to claim 3, The triheadon is bent at an angle of 135 degrees at the upper and lower edges and the side edges, Membrane type LNG storage tank, characterized in that the mounting length of one side of the triheadon is 0.71-0.78 m. The method according to claim 1, The membrane type LNG storage tank is a membrane type LNG storage tank, characterized in that the GTT NO 96 storage tank. The method according to claim 1, The triheadron includes upper and lower triheadrons extending in both directions between the upper and lower walls and the chamfers at the upper and lower edges of the upper and lower walls and the chamfers, and at the side edges of the sidewalls forming the chamfers. A lateral triheadron extending in both directions across the sidewall and the chamfer, facing the front and rear walls, The upper and lower triheadron and the side triheadron membrane type LNG storage tank, characterized in that connected to each other by a connector. The method according to any one of claims 1 to 6, The floating offshore structure is any one selected from the LNG FPSO, LNG FSRU, LNG transport ship and LNG RV, which is used in the floating state at the flow where the flow occurs while having a storage tank for storing the liquid cargo loaded in the cryogenic state Membrane type LNG storage tank, characterized in that. Membrane type LNG storage tank installed in the floating offshore structure to store LNG, The support structure for supporting the sealing wall and the insulating wall constituting the storage tank between the edges including the chamfer of which the length is reduced and at the same time reducing the length of the chamfer of the storage tank is composed of triheadron without invar tube. Membrane type LNG storage tank, characterized in that.

Images