KR101076267B1 - Floating structure with a intermediate loading tank - Google Patents

Abstract

The present invention relates to a floating structure having a storage tank capable of storing liquefied natural gas (Liquefied Natural Gas; LNG), and more particularly, having a structure capable of withstanding the impact of sloshing during intermediate loading. A floating structure with a storage tank that can be operated in a loaded state.

According to the present invention, a floating structure having a storage tank capable of storing liquid cargo and used in a floating state at sea, can withstand the impact of sloshing even when it is in an intermediate loading state during loading or unloading of liquid cargo. A floating structure is provided, comprising an interloadable dedicated tank for loading the vessel having a structure capable of loading.

Floating Structures, Loading, Unloading, Interim Loading, Membrane Type Storage Tanks, Freestanding Storage Tanks, Two-Row Layout, Sloshing, Copper Dams

Description

FLOATING STRUCTURE WITH A INTERMEDIATE LOADING TANK}

The present invention relates to a floating structure having a storage tank capable of storing liquefied natural gas (Liquefied Natural Gas; LNG), and more particularly, having a structure capable of withstanding the impact of sloshing during intermediate loading. A floating structure with a storage tank that can be operated in a loaded state.

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 at cryogenic temperatures (approximately -163 ° C), and its volume is reduced to approximately 1/600 of that of natural gas, making it well suited for long-distance transport through the sea.

LNG carriers for loading LNG into the sea 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 of cargo directly affects the insulation.

Independent tank type storage tanks are either 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 primary sealing wall 10 is leaked, the cargo is secured only by the secondary sealing wall for a considerable period of time. It can support. 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 (ie, an insulation wall).

Meanwhile, the Mark III type storage tank includes a primary sealing wall made of a 1.2 mm thick stainless steel membrane, a secondary sealing wall made of a triplex, a polyurethane foam, and the like. The primary heat insulating wall and the secondary heat insulating wall formed 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 membrane-type liquefied natural gas storage tank may be more vulnerable to a sloshing problem because it is difficult to install a reinforcing member inside. 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.

Since the sloshing phenomenon inevitably occurs during the operation of the ship or mooring the floating structure, it is necessary to design the storage tank structure to have sufficient strength to withstand the impact force due to the sloshing.

Accordingly, a membrane type storage tank has been proposed in which upper and lower chamfers are inclined at approximately 45 degree angles on the upper and lower sides of the tank to withstand the impact force due to sloshing. In the case of a conventional storage tank having a chamfer, the problem due to the sloshing phenomenon can be solved to some extent, but this alone has a limit in dealing with the impact force due to the gradually increasing storage tank or sloshing during intermediate loading.

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

The LNG FPSO is a floating structure used to directly liquefy the produced natural gas at sea and store it in an LNG storage tank and, if necessary, to transfer LNG stored in the LNG storage tank to an LNG carrier. In addition, the LNG FSRU is a floating structure that stores LNG unloaded from LNG carriers in an LNG storage tank at sea far from the land, and then vaporizes LNG as needed to supply land demand.

In the case of LNG carriers, the load due to sloshing is most important when the LNG is in an intermediate loading state where the LNG is partially loaded by about 30 to 50%. The LNG was to be filled in storage tanks or operated completely empty.

However, floating structures such as LNG FPSOs or LNG FSRUs are used in a floating state, anchored at a predetermined position on the sea, and are influenced by external variables such as production in gas fields, demands from customers, and supply of LNG to LNG carriers. Since the loading amount of the LNG storage tank is changed, there is a problem that it is not possible to arbitrarily adjust the amount of LNG to be stored, so that the intermediate loading state in which the impact force due to sloshing acts the most cannot be avoided. Therefore, there is a demand for reinforcement or operation methods in preparation for intermediate loading.

LNG carriers also need to ship or unload cargo (eg LNG) from another LNG carrier or offshore plant. In this case, the LNG storage tank in the LNG carrier may be in an intermediate loading state, and when the movement of the LNG carrier becomes severe due to waves or waves, the impact force due to sloshing may increase, which may damage the LNG storage tank. Therefore, even in the case of LNG carriers, there is a demand for minimizing sloshing during intermediate loading occurring during loading and unloading.

On the other hand, in order to prepare for the impact force due to sloshing and to ensure the stability of the bowing area sensitive to polar operating conditions and to provide a space for regasification equipment on the upper deck of the bow, the bow is strong in the bow. A plurality of independent storage tanks are installed, and a method of installing a membrane type storage tank with low manufacturing cost is proposed in the remaining positions.

However, this method does not take into consideration that the bow and stern are sensitive to sloshing during the loading or unloading of LNG. Instead, a standalone storage tank is installed only in the bow to reinforce strength. In this case, there is a problem that the membrane-type storage tank at the stern portion or the middle of the hull is still exposed to the risk of damage to the storage tank by sloshing during shipping and unloading at sea.

The present invention for solving the conventional problems, loading and unloading liquid cargo, such as LNG is possible to load-only intermediate loading that can withstand the impact due to sloshing even when the storage tank is in the intermediate loading state By providing a floating structure with a tank, it is intended to reduce the time the normal membrane type tanks other than the intermediate stackable tank are exposed to the intermediate stack state.

According to an aspect of the present invention for achieving the above object, a floating structure having a storage tank for storing liquid cargo and used in a floating state at sea, in the intermediate loading state during the loading or unloading of the liquid cargo A floating structure is provided, including a loading-only intermediate loading tank having a structure capable of withstanding the impact of sloshing even when present.

Preferably, the floating structure includes a plurality of storage tanks, and at least one of the plurality of storage tanks is the intermediate stackable tank.

Among the plurality of storage tanks, the remaining storage tank except for the intermediate stackable tank is preferably a general membrane type storage tank.

The intermediate stackable tank is preferably a two-row batch type membrane storage tank in which a pair of storage tanks are divided into left and right by longitudinal cofferdams installed along the longitudinal direction of the floating structure.

The cofferdam is preferably provided with a fluid passage for connecting the pair of the membrane-type storage tanks arranged in two rows.

The intermediate stackable tank is preferably a stand-alone storage tank.

The floating structure preferably includes a main pipeline for directly connecting a plurality of the storage tanks separately, and an unloading pipeline connected to the main pipeline for unloading the liquid cargo contained in the storage tank. .

The floating structure preferably comprises a shipping pipeline connected to the main pipeline for loading liquid cargo into the storage tank.

The liquid cargo is LNG, and the floating structure preferably includes a regasification device for regasifying LNG unloaded from the intermediate stackable tank.

The floating structure is installed inside the intermediate stackable tank to unload the liquid cargo contained in the intermediate stackable tank, or the liquid cargo is stored in the remaining storage tanks other than the intermediate stackable tank among the plurality of storage tanks. It is preferred to include a pump for delivery.

Preferably, the floating structure includes a pump installed in the remaining storage tanks other than the intermediate stackable tank among the plurality of storage tanks to transfer the liquid cargo contained in the remaining storage tank to the intermediate stackable tank. .

The floating structure is preferably any one selected from LNG carriers, LNG RV and LNG FPSO.

According to another aspect of the present invention, there is provided a floating structure which can store a liquid cargo and is used in a floating state at sea, the membrane-type storage tank being installed in the floating structure to store the liquid cargo; A loading-only tank installed in the floating structure to store and carry out the liquid cargo at the same time; A transfer pump installed in the membrane type storage tank to transfer the received liquid cargo to the ship's dedicated tank; Unloading is installed in the dedicated loading tank and used for unloading the liquid cargo contained in the dedicated loading tank when unloading and used to deliver the liquid cargo contained in the dedicated loading tank to the membrane storage tank at the time of shipment Pump; It includes, The loading and unloading tank is provided with a floating structure characterized in that it has a structure capable of withstanding the impact due to sloshing even when in the intermediate loading state during the loading or unloading liquid cargo.

According to the present invention as described above, there is provided a loading-only intermediate loading tank that can withstand the impact of sloshing even when the storage tank is in the intermediate loading state, such as during the loading or unloading of liquid cargo such as LNG Floating structures may be provided.

In addition, according to the floating structure of the present invention, the loading and unloading of the liquid cargo can be made through the tank loading dedicated tank that can withstand the impact of the sloshing during intermediate loading, the state of high risk of sloshing Damage to the LNG storage tank can be prevented even during intermediate loading just before and after the ballast.

In addition, according to the floating structure of the present invention, it is possible to minimize the time that the general membrane-type tank is exposed to the intermediate loading state by using a loading-only intermediate loading tank, the normal membrane-type tank may be damaged by sloshing Risks can be minimized.

In addition, according to the present invention, since most storage tanks installed in the floating structure can be manufactured as a general membrane type tank, it is cost competitive, and by operating a tank that can be interposed, it is possible to operate and moor, as well as the time of loading of cargo. Safe floating structures can be provided.

Hereinafter, a floating structure according to a preferred embodiment of the present invention will be described in detail with reference to the drawings.

In the present specification, the floating structure is a concept including both a structure and a vessel that are used while floating in a sea where a flow occurs while having a storage tank for storing a liquid cargo loaded at a cryogenic state such as LNG, for example This 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 (FSRUs).

FIG. 1 is a schematic side view of a floating offshore structure with an intermediate stackable tank dedicated for loading and unloading, according to the present invention. FIG. 2 shows an example of a case in which a two-row arrangement membrane storage tank is installed at the stern as an intermediate stackable tank, and FIG. 3 is a cross-sectional view of the two-row arrangement membrane storage tank. Figure 4 shows an example of the case where the independent storage tank is installed in the second tank from the bow as the intermediate stackable tank.

5 to 8 sequentially illustrate a method of unloading LNG from a storage tank including an intermediate stackable tank, and FIG. 9 illustrates a method of loading LNG.

As shown in the figure, the floating structure according to the present invention, the loading and unloading dedicated to withstand the impact due to sloshing even when the storage tank is in the intermediate loading state, such as during the loading or unloading of liquid cargo, such as LNG Has an intermediate stackable tank (1).

As the intermediate stackable tank 1, the sloshing tank 1 is not injured by sloshing even when it is in the intermediate stacking state where the impact force due to the sloshing is most applied, that is, when the LNG is partially loaded by about 30 to 50%. However, storage tanks with stronger or improved structure than conventional membrane storage tanks are employed.

For example, as shown in Figs. 2 and 3, as the intermediate stackable tank 1, a pair of membrane storage tanks arranged in two rows may be employed. A pair of membrane-type storage tanks arranged in two rows may be divided left and right by a longitudinal cofferdam 11 installed along the longitudinal direction of the floating structure. The longitudinal cofferdam 11 is a lattice-like structure in which a void space is provided inside, similarly to a transverse cofferdam provided in front and rear of each membranous storage tank.

In the present invention, the intermediate stackable tank (1) consisting of a pair of storage tanks arranged in two rows is a membrane type storage tank, and thus the longitudinal copper as a structure for arranging a pair of storage tanks in two rows in the left and right directions. The dam 11 is used. The intermediate stackable tank 1 may have a structure in which two storage tanks are arranged in two rows substantially in the width direction of the floating structure by the longitudinal cofferdam 11, and the longitudinal cofferdam 11 ( That is, the storage tanks formed so as to be arranged in two rows on both sides with a space portion therebetween can secure separate storage spaces, each of which is completely sealed by the membrane structure.

By arranging the storage tanks in two rows, the amount of liquid cargo stored in one storage space is reduced, and as the width of the storage tank is reduced, the natural period of motion of the liquid cargo moves away from the natural period of motion of the floating structure. The magnitude of the motion of the cargo can be reduced. Accordingly, the impact force due to sloshing applied to the storage tanks arranged in two rows can be drastically reduced.

According to the invention, it is preferable that a fluid passage is formed between the two storage tanks arranged in two rows for use as the intermediate stackable tank 1 to connect the two storage tanks to each other. The fluid passage includes a lower fluid passage 12 for penetrating the lower portion of the longitudinal cofferdam 11 so that the liquid LNG can flow freely between the two storage tanks. In addition, the fluid passage is an upper fluid passage for allowing LNG, ie, BOG (Boil Off Gas), which has evaporated into a gaseous state through the upper portion of the longitudinal cofferdam 11 to flow freely between the two storage tanks. It may further include (13).

As such, when the fluid passage, in particular the lower fluid passage 12, is formed, the liquid LNG can move between both storage spaces of the intermediate stacking tank 1, so that the LNG stored in the intermediate stacking tank 1 Even if only one facility, such as the unloading pump 1a, the piping (not shown), and the pump tower (not shown), which can be discharged to the outside, is installed, all LNG in the intermediate stackable tank 1 can be discharged. For this purpose, the lower fluid passage 12 is preferably formed so as to be adjacent to the bottom of the cofferdam, ie the bottom of the intermediate stackable tank 1.

In addition, as shown in FIG. 4, as the intermediate stackable tank 1, a standalone storage tank may be employed. Stand-alone storage tanks are stronger in strength than membrane-type storage tanks and can withstand the impact of sloshing, but have a disadvantage in that the manufacturing cost is high. According to one embodiment of the present invention, a strong independent stand-alone storage tank is used as a loading-only intermediate stackable tank (1), while the remaining storage tank uses a membrane type storage tank having a relatively low manufacturing cost, and thus a low manufacturing cost. Yet providing a floating structure that can withstand the impact of sloshing.

2 and 4, it is shown that one intermediate stackable tank 1 is installed inside the floating structure and four general membrane type tanks 3 are installed, but are installed in the floating structure. Of course, the number of intermediate tanks can be installed more than one if necessary.

In addition, the intermediate stackable tank 1 is illustrated as being located on the stern side in the case of FIG. 2, and is illustrated as being located second from the bow side in the case of FIG. It is not limited to only the installation position shown in the installation position of the intermediate stackable tank (1) can be appropriately determined as necessary.

According to the present invention, all LNG is loaded and unloaded through the intermediate stackable tank 1 installed in the floating structure. That is, the intermediate stackable tank 1 is utilized as a ship-only tank so that all the LNG in the remaining general membrane type tank 3 is shipped or unloaded through the intermediate stackable tank 1.

To this end, a floating structure with an intermediate stackable tank 1 according to the invention comprises a main pipeline L1 to which the intermediate stackable tank 1 and the general membrane type tank 3 are directly connected, And a loading pipeline L2 for unloading the LNG from the floating structure, and a loading pipeline L3 for loading the LNG into the floating structure.

However, if necessary, the unloading pipeline may serve as the shipping pipeline. An example of a floating structure that carries out loading and unloading operations through one pipeline includes, for example, an LNG carrier.

The main pipeline L1 is divided into two lines inside each storage tank (ie, an intermediate stackable tank and a general membrane type tank). These two lines are a filling line for supplying LNG to the storage tank at shipment, and a discharging line for discharging LNG from the storage tank at unloading. At the end of the discharge line pumps 1a and 3a are provided. Only one line may be installed inside the storage tank so that the filling line can serve as the discharge line as needed in the design.

An unloading pump 1a is installed in the intermediate loading tank 1 for loading and unloading only to unload the housed LNG to the outside of the floating structure. In each general membrane type tank 3, a transfer pump 3a for transferring the contained LNG to the intermediate stackable tank 1 is provided. The unloading pump 1a and the transfer pump 3a are preferably installed at the end of the main pipeline L1, more particularly at the end of the discharge line of the main pipeline. That is, an unloading pump 1a is installed at the end of the main pipeline L1 in the intermediate stackable tank 1, and a transfer pump 3a at the end of the main pipeline L1 in the general membrane type tank 3. Is installed.

The regasification apparatus 5 is connected to the unloading pipeline L2, which may be installed on a floating structure such as, for example, an LNG RV or an LNG FSRU, or, for example, with an LNG carrier. Likewise, it may be used to be installed outside the floating structure. The natural gas regasified by the regasification apparatus 5 can continue to be supplied to each customer.

Hereinafter, the LNG unloading operation and shipping operation method of the floating structure according to the present invention having an intermediate stackable tank 1 will be described with reference to FIGS. 5 to 9.

FIG. 5 shows a state in which all the tanks of the floating structure (the intermediate stackable tank 1 and the general membrane type tank 3) are filled with liquid cargo such as LNG. In FIG. 5, the intermediate stackable tank 1 is shown to be located at the leftmost side, but as described above, the position of the intermediate stackable tank 1 may be changed as necessary in design.

FIG. 6 shows a state in which all the LNG loaded through the main pipeline L1 and the unloading pipeline L2 are unloaded from the leftmost intermediate stackable tank 1. As shown in FIG. 6, the unloading operation starts from the intermediate stackable tank 1.

At the time of unloading, the unloading conditions change according to the conditions of the natural gas demand source. In other words, there may be a case where continuous unloading is impossible such as unloading work is interrupted according to the requirements of the customer. In addition, since the unloading operation must be performed at the unloading speed determined according to the terminal condition of the demand destination, the LNG cannot be supplied in accordance with the design flow rate of the pump installed inside the tank, and the LNG must be supplied at a speed lower than that. Can be. Discontinuous unloading operations and slow LNG pumping consequently increase the time that the storage tank is exposed to intermediate loading and increase the risk of damage to the storage tank by impact forces due to sloshing during intermediate loading.

According to the present invention, since the loading operation is made using the intermediate loading tank (1) capable of withstanding the impact force due to the sloshing during the intermediate loading, the loading stops during the loading operation is stopped or the loading speed is late, Long exposure to conditions can prevent damage to the storage tank.

After unloading all of the LNG housed in the intermediate stackable tank 1, all the LNG housed in one of the general membrane tanks 3 is transferred to the intermediate stackable tank 1, as shown in FIG. To pass. In this case, the LNG is transferred through the main pipeline L1 by a transfer pump 3a installed inside the general membrane type tank 3, and the transfer operation is performed according to the maximum transfer flow rate of the transfer pump 3a. Since the intermediate loading time of the general membrane type tank 3 can be shortened, it is preferable.

In addition, since the operation of delivering the LNG contained in the general membrane type tank 3 to the intermediate stackable tank 1 is performed in the floating structure, it is not necessary to consider the conditions of the destination and the transfer pump 3a. The transfer operation can be completed continuously in the maximum time as long as the flow rate of the tolerant permits.

When all the LNG of the general membrane type tank 3 is transferred to the intermediate stackable tank 1, the LNG is unloaded from the intermediate stackable tank 1 in the manner as shown in FIG. This operation is repeated to unload the LNG of all common membrane tanks 3 through the intermediate stackable tank 1.

In FIG. 8, almost all LNG contained in the floating structure is unloaded so that the storage tanks 1 and 3 installed in the floating structure are completely emptied. In general, the kinetic characteristics of the floating structure are worst under all storage tanks being empty or with minimal cargo, ie ballast conditions. In other words, since the total weight of the floating structure including the weight of the cargo is the lightest, the floating structure is most sensitive to the effects from wind, waves and waves.

Therefore, the most dangerous condition in which the impact force due to the sloshing phenomenon is maximized in the floating structure is an intermediate loading state just before completing the unloading as shown in FIG. 8. According to the present invention, since all the LNG contained in the general membrane type tank 3 is unloaded and the final unloading operation is performed by using the intermediate stackable tank 1, the intermediate load just before the ballast is loaded by the loading only. Will only occur in the possible tank (1).

Since the intermediate stackable tank 1 of the present invention is designed to withstand the impact force due to the sloshing as described above, it is possible to reliably prevent damage due to the sloshing even during the intermediate stacking just before the ballast. In addition, it is possible to completely prevent the condition that the ordinary membrane tank 3 is exposed to the intermediate loading state immediately before the ballast.

Meanwhile, FIG. 9 shows a state in which the storage tanks 1 and 3 start to ship LNG to the floating structure in which the storage tanks 1 and 3 are completely empty. When the LNG is loaded, the LNG is supplied from the external LNG supply source (not shown) to the intermediate loading-capable tank 1 dedicated to the loading through the LNG loading pipeline L3 and the main pipeline L1.

Like the state shown in FIG. 8, since the state immediately after the start of the loading operation shown in FIG. 9 is also a ballast condition, this is also the most dangerous condition in which the impact force due to the sloshing phenomenon is maximized in the floating structure.

According to the present invention, since the initial loading operation is first performed using the intermediate stackable tank 1 before the LNG is loaded into the general membrane type tank 3, the intermediate stacking immediately after the ballast is possible for the intermediate loading of the loading only. It occurs only in the tank (1).

Since the intermediate stackable tank 1 of the present invention is designed to withstand the impact force due to sloshing as described above, it is possible to reliably prevent damage due to sloshing even during intermediate loading immediately after the ballast. In addition, it becomes possible to completely prevent the condition that the ordinary membrane tank 3 is exposed to the intermediate loading state immediately after the ballast.

In contrast to the unloading, if the intermediate stackable tank 1 is completely filled with LNG during the loading operation, the LNG is loaded into the main pipeline L1 by using the unloading pump 1a installed inside the intermediate stackable tank 1. Through one of the ordinary membrane tank (3). When all of the LNG in the intermediate stackable tank 1 is transferred to one of the general membrane type tanks 3, the ship is loaded again from the external LNG supply source (not shown) through the LNG loading pipeline L3 and the main pipeline L1. LNG is supplied to the intermediate stackable tank (1) for the enemy.

This operation is repeated to complete the shipment of LNG to all storage tanks 1 and 3 in the floating structure.

According to the present invention, since the loading operation is performed using only the intermediate stackable tank 1 capable of withstanding the impact force due to the sloshing during the intermediate loading, as in the unloading, the shipment is performed during the loading operation. In the event of this interruption or slow shipping speeds, long exposures to intermediate loads can prevent damage to the storage tank.

In addition, since the operation of delivering the LNG contained in the intermediate stackable tank 1 to the general membrane type tank 3 is performed in the floating structure, it is not necessary to consider external conditions. The transfer operation can be completed continuously in the fastest time as the transfer flow permits.

As described above, the floating structure having an intermediate stackable 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 is seen within the claims. Various modifications and variations can be made by those skilled in the art to which the invention pertains.

1 is a schematic side view of a floating offshore structure with an intermediate stackable tank dedicated for loading and unloading, in accordance with the present invention;

Figure 2 is an illustration of a case where a two-row arrangement type membrane storage tank is installed at the stern as the intermediate stackable tank of the present invention,

3 is a cross-sectional view of a two-row batch type membrane storage tank,

Figure 4 is an illustration of the case of installing a stand-alone storage tank in the tank 2, the second from the bow as the intermediate stackable tank of the present invention,

5 to 8 are views for sequentially explaining a method for unloading LNG from the floating structure of the present invention having a storage tank including an intermediate stackable tank, and

9 is a view for explaining a method for loading LNG to the floating structure of the present invention.

Description of the Related Art

1: Intermediate Loading Tank 1a: Unloading Pump

3: general membrane tank 3a: transfer pump

5: regasification apparatus 11: longitudinal cofferdam

12: lower fluid passage 13: upper fluid passage

L1: main pipeline L2: unloading pipeline

L3: Shipping Pipeline

Claims (13)

A floating structure having a storage tank for storing liquid cargo and used in a floating state at sea, It includes a loading-only intermediate loading tank capable of withstanding the impact of sloshing even when in the intermediate loading state during the loading or unloading of liquid cargo, The intermediate stackable tank is a two-row arrangement type membrane type having separate storage spaces, each sealed by a pair of storage tanks arranged left and right by longitudinal cofferdams installed along the longitudinal direction of the floating structure. Floating structure, characterized in that the storage tank. The method according to claim 1, The plurality of storage tanks are installed in the floating structure, at least one of the plurality of the storage tank is a floating structure, characterized in that the intermediate stackable tank. The method according to claim 2, Floating structure, characterized in that the remaining storage tank of the plurality of storage tanks except the intermediate stackable tank is a general membrane type storage tank. delete delete delete The method according to claim 2, And a main pipeline for directly connecting a plurality of said storage tanks separately, and a unloading pipeline connected to said main pipeline for unloading liquid cargo contained in said storage tank. The method of claim 7, And a shipping pipeline connected to said main pipeline for loading liquid cargo into said storage tank. The method according to claim 1, Wherein said liquid cargo is LNG and said floating structure comprises a regasification device for regasifying LNG being unloaded from said intermediate loadable tank. The method according to claim 1, The floating structure is a floating structure, characterized in that any one selected from LNG carriers, LNG RV and LNG FPSO. The method according to any one of claims 1, 2, 3, 7, 8, 9 and 10, A pump installed in the intermediate stackable tank to unload the liquid cargo contained in the intermediate stackable tank or to deliver the liquid cargo to a storage tank other than the intermediate stackable tank among the plurality of storage tanks. Floating structure, characterized in that. The method according to any one of claims 1, 2, 3, 7, 8, 9 and 10, And a pump installed in the remaining storage tanks other than the intermediate stackable tank among the plurality of storage tanks to transfer the liquid cargo contained in the remaining storage tank to the intermediate stackable tank. A floating structure that can store liquid cargo and is used floating at sea. A membrane type storage tank installed in the floating structure to store liquid cargo; A loading-only tank installed in the floating structure to store and carry out the liquid cargo at the same time; A transfer pump installed in the membrane type storage tank to transfer the received liquid cargo to the ship's dedicated tank; Unloading is installed in the dedicated loading tank and used for unloading the liquid cargo contained in the dedicated loading tank when unloading and used to deliver the liquid cargo contained in the dedicated loading tank to the membrane storage tank at the time of shipment Pump; Including; The lading tanks are paired by longitudinal cofferdams installed along the longitudinal direction of the floating structure so that they can withstand the impact of sloshing even when in the middle of loading or unloading liquid cargo. The storage tank of the floating structure, characterized in that the two-row arrangement type membrane storage tank having a separate storage space, each of which is arranged by being divided into left and right.

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