WO2015012577A1 - Floating marine structure and method for controlling temperature thereof - Google Patents

Abstract

The present invention relates to a floating marine structure and a method for controlling the temperature thereof, the floating marine structure, more specifically, characterized by comprising cofferdams provided between a plurality of LNG storage tanks disposed in one or more rows in the length-wise direction of a ship, wherein the cofferdams are controlled to be at sub-zero temperatures to reduce the boil-off rate (BOR) arising due to the transfer of heat from the cofferdams to the interior of the plurality of LNG storage tanks.

Description

Method of temperature control of floating offshore structures and floating offshore structures

The present invention relates to a floating offshore structure and a temperature control method of the floating offshore structure, and more particularly, to reduce the heat transfer between the copper dam and the LNG stored in the LNG storage tank to reduce the BOR (Boil-off Rate) The present invention relates to a floating offshore structure and a temperature control method of the floating offshore structure.

Generally, natural gas is transported in gaseous state through onshore or offshore gas piping, or stored in LNG carriers in the form of liquefied liquefied natural gas (LNG). Is carried.

Such LNG is obtained by cooling natural gas to cryogenic temperature, for example, approximately -163 ° C., and its volume is reduced to approximately 1/600 than that of natural gas in gas state, and thus is suitable for long distance transportation through sea.

Such LNG may be transported through the sea in LNG carriers to be unloaded at land requirements, or may be transported through the sea in LNG RV (LNG Regasification Vessel) to reach the land requirements and then regasified to be unloaded as natural gas. LNG carriers and LNG RVs are equipped with LNG storage tanks (also called cargo holds) that can withstand the cryogenic temperatures of LNG.

In addition, there is an increasing demand for offshore structures such as LNG Floating, Production, Storage and Offloading (FPSO) and LNG Floating Storage and Regasification Units (FSRUs). Tank is included.

Here, LNG FPSO is a marine structure used to directly liquefy the produced natural gas in the sea to store in the storage tank, and to transport the LNG stored in the storage tank to the LNG carrier if necessary.

LNG FSRU is an offshore structure that stores LNG unloaded from LNG carriers in a storage tank at a distance far from the land, and then vaporizes LNG as needed to supply it to land demand.

Such LNG storage tanks are classified into independent tank type and membrane type according to whether the insulation material for storing LNG at low temperature directly affects the load of cargo. The tank is divided into MOSS type and IHI-SPB type, and the membrane type storage tank is divided into GT NO 96 type and TGZ Mark III type.

GT NO 96, a membrane type of conventional LNG storage tanks, has a primary barrier and a secondary barrier made of Invar steel (36% Ni) 0.5 to 0.7 mm thick. It is installed in two layers on the inner surface, the primary sealing wall is located on the LNG side, the secondary sealing wall is installed so as to be located on the inner surface side of the hull to wrap the LNG double.

In addition, the primary insulation wall is installed in the space between the primary sealing wall and the secondary sealing wall, and the secondary insulation wall is installed in the space between the secondary sealing wall and the inner hull. The wall minimizes the transfer of heat from the LNG storage tank to the LNG.

Meanwhile, since LNG stored in the LNG storage tank is stored at about -163 ° C., which is a vaporization temperature at atmospheric pressure, when heat is transferred to LNG, LNG is vaporized to generate boil off gas (hereinafter referred to as 'BOG').

In the case of the membrane type LNG storage tank, if the cold LNG storage tank is continuously installed, the temperature of steel in between may drop sharply and brittle fracture may occur.

To prevent this, a space called a cofferdam is provided between LNG storage tanks to prevent damage caused by low temperature of LNG.

However, even if the cofferdam is installed, the temperature of the steel of the cofferdam bulkhead member in contact with the LNG cargo hold drops by -60 ℃ or less by cryogenic LNG. Common steels are damaged by cold brittleness when exposed to -60 ° C.

As a countermeasure, the cofferdam can be made of cryogenic materials such as stainless steel or aluminum, but the use of cryogenic materials can dramatically increase the price of ships.

Therefore, when the cofferdam and the LNG storage tank is installed, the temperature of the cofferdam is controlled to 5 ° C, and the bulkhead of the cofferdam is manufactured from relatively inexpensive steel that withstands the room temperature.

In the case of existing LNG carriers, when the temperature of the cofferdam is below 5 ° C, the heating system operates and always maintains above 5 ° C. Existing LNG carriers are equipped with glycol heating systems or electric heating systems for this purpose.

Therefore, existing LNG carriers are always designed / operated with a cofferdam temperature of at least 5 ° C or higher, and BOR is generated under these temperature conditions.

Currently, LNG carriers are sensitive to BOR figures at the stage of contracting. For example, in the past, 0.15% BOR was the contract condition, but recently, BOR at 0.125%, 0.10%, or 0.095% has been proposed as the contract condition.

However, current membrane type tanks have a thermal insulation wall installed in the cargo hold. Since the LNG Cargo insulation wall must be able to withstand the heat transfer performance and the load transferred from the LNG cargo to the cargo hold, changing the insulation wall of the existing LNG cargo hold to increase the insulation performance, a lot of research, design changes and cost increase .

Indeed, even if there are LNG cargo insulation walls that satisfy the BOR of 0.13%, a lot of studies, periods, and costs are incurred to reduce the BOR by 4% when 0.125% is the owner's BOR requirement.

In addition, even if there is a LNG cargo insulation wall that guarantees a 0.103% BOR, if a ship owner presents a BOR of 0.10%, the LNG carriers cannot be applied, and thus, LNG carriers cannot be ordered. The LNG carrier market is now able to compete in a favorable order in ship orders if the BOR is reduced by 1%.

On the other hand, the technical development to reduce the existing BOR is to improve the performance of the LNG cargo insulation wall. Since the current market demands a small BOR of 1%, a popular method at this point is to increase the thickness of LNG cargo hold.

However, increasing the thickness of the LNG cargo hold reduces the volume of LNG storage. Or, the ship size is increased to maintain the same cargo hold volume.

In addition, since the cargo hold becomes structurally weaker as the thickness of the hold increases, studies to reinforce it are to be carried out.

Accordingly, the technical problem to be achieved by the present invention is to provide a floating offshore structure that can reduce the BOR at a low cost by lowering the control temperature of the cofferdam and by designing and manufacturing a cofferdam bulkhead with a corresponding steel grade.

Another technical problem to be achieved by the present invention is to reduce the BOR at a low cost by lowering the control temperature of the cofferdam, floating type that can adjust the control temperature of the cofferdam in accordance with the type of operation and operation conditions controlled to sub-zero temperature It is to provide an offshore structure and a temperature control method.

Another technical problem to be achieved by the present invention is to reduce the BOR at a low cost by lowering the control temperature of the cofferdam, to provide a floating offshore structure that can easily check the hot spot of the cofferdam.

Another technical problem to be achieved by the present invention is to provide a floating offshore structure that can reduce the BOR by reducing heat transfer through the bulk head and satisfy the required structural strength.

According to an aspect of the present invention, a copper dam is provided between a plurality of LNG storage tanks installed in one row or more in the longitudinal direction of the hull, the cofferdam is controlled to a sub-zero temperature, from the cofferdam Floating offshore structure may be provided that reduces the BOR (Boil-off Rate) generated by heat transfer to the interior of the plurality of LNG storage tanks.

The cofferdam may include: a pair of bulk heads spaced apart from each other between the plurality of LNG storage tanks; And a space portion provided by the pair of bulk heads and the inner wall of the hull, and the pair of bulk heads can be controlled to a sub-zero temperature.

The pair of bulk heads may be made of at least one of B, D, E, AH, DH and EH, which are steel grades defined by IGC.

The pair of bulk heads may be made of low temperature steel (LT) applied at -30 ° C or less.

The pair of bulk heads are controlled at -30 to -20 ° C and can be made of E or EH, a steel grade defined by IGC.

The gas supply unit may further include a gas supply unit supplying gas into the cofferdam to prevent the inside of the cofferdam from being damaged by freezing of moisture in the air.

The gas supply unit is provided in the hull supply pipe for supplying the gas into the cofferdam; A discharge pipe provided in the cofferdam to discharge the internal gas of the cofferdam to the outside of the cofferdam; And it may include a valve provided in the supply pipe and the discharge pipe.

The gas may include one or more of dry air, inert gas, and N ₂ gas.

And a heating unit provided at the cofferdam to heat the cofferdam, wherein the cofferdam is controlled to a sub-zero temperature and generated by heat transfer from the cofferdam into the plurality of LNG storage tanks. The sub-zero temperature may be changed to a specific temperature including the temperature of the image by heating the heating unit.

If the bulkhead of the cofferdam is made of a material that can withstand up to -30 ~ 0 ℃ the cofferdam may be varied in the range of -30 ~ 70 ℃.

When the bulkhead of the cofferdam is made of low temperature steel that can withstand up to -55 ° C, the cofferdam may be varied in the range of -55 to 70 ° C.

When the fuel consumption of the floating offshore structure is large, the temperature of the cofferdam is increased to increase the generation of BOG (Boil-off Gas) to be used as fuel, and when the fuel consumption of the offshore structure is small, the temperature of the cofferdam is increased. Lowering can reduce the occurrence of the BOG.

The cofferdam may be heated by the heating unit to allow the worker to enter the cofferdam, thereby controlling the cofferdam temperature to a specific temperature including an image.

The sub-zero temperature of the cofferdam may be changed to a specific temperature including the temperature of the image by the high temperature dry air supplied into the cofferdam.

The floating offshore structure lowers the set temperature of the cofferdam when the internal pressure of the LNG storage tank is greater than the set pressure of the LNG storage tank, and when the internal pressure of the LNG storage tank is less than the set pressure of the LNG storage tank. The set temperature of the cofferdam can be increased.

The heating unit heats at least one of a trunk deck space controlled to a sub-zero temperature and a side passage way in contact with the trunk deck to heat the trunk deck space and the side passages of the image. Temperature can be varied to a certain temperature, including temperature.

The floating offshore structure may further include a heat insulator provided in the cofferdam.

The cofferdam includes a plurality of lateral cofferdams for dividing the plurality of LNG storage tanks in a lateral direction, and the heat insulating material is a foremost front bulkhead of a lateral cofferdam disposed at the foremost front of the plurality of lateral cofferdams. It may be provided in the stern rearmost bulkhead of the transverse cofferdam disposed in the head and stern rearward, respectively.

The insulation may include at least one of an insulation wall for insulating the LNG stored in the plurality of LNG storage tanks, a panel type insulation, a foam type insulation, a vacuum insulation or particle type insulation and a nonwoven insulation. .

It may further include a heat insulating material damage prevention member provided on the bottom of the cofferdam to prevent damage of the heat insulating material.

The floating offshore structure may further include a gas supply unit supplying gas to the cofferdam.

The gas supply unit may include: a gas supply pipe provided in the cofferdam to supply gas supplied through a gas supply line into the cofferdam; A gas discharge pipe provided in the cofferdam to discharge the internal gas of the cofferdam to the outside of the cofferdam; And an on / off valve provided in the gas supply pipe and the gas discharge pipe.

The gas supplied into the cofferdam has a dew point temperature of -45 ~ -35 ℃, the pair of bulk head can be controlled 1 ~ 10 ℃ higher than the dew point temperature of the gas.

While continuously injecting and venting the gas into the cofferdam, the temperature of the cofferdam may be maintained as an image, but the gas may have an image temperature.

By continuously injecting and discharging the gas into the cofferdam, the temperature of the cofferdam may be increased to provide an environment in which an operator may enter the cofferdam.

The gas supply unit supplies the gas to at least one of a trunk deck space controlled to a sub-zero temperature and a side passage way in contact with the trunk deck, wherein the dew point temperature of the gas is equal to the trunk temperature. It may be lower than the temperature of the deck space and the side passage.

The gas may include dry air.

The bulk head is not extended to the outer hull but is connected only to the inner hull, and the strength member connecting the outer hull and the inner hull is not connected to the bulk head so that the LNG stored in the bulk head and the plurality of LNG storage tanks. The BOR (Boil-off Rate) generated by heat transfer of the liver can be reduced.

The bulk head is controlled at a temperature of −163 to −50 ° C., and may be made of a cryogenic material including aluminum or stainless steel.

The floating offshore structure further includes a sealing and insulating unit provided in the plurality of LNG storage tanks to seal and insulate the LNG, wherein the sealing and insulating unit is in a region where the plurality of LNG storage tanks and the bulk head are in contact with each other. The bulk head may not be provided.

The floating marine structure may be provided with a space between the bulkhead and the inner hull disposed at the foremost front and the rear of the stern, the insulation may be provided in the space.

The insulation may include at least one of an insulation wall for insulating the LNG stored in the plurality of LNG storage tanks, a panel type insulation, a foam type insulation, a vacuum insulation or particle type insulation and a nonwoven insulation. .

The inner hull may be made of a cryogenic material.

The floating offshore structure may be any one selected from an LNG carrier, an LNG FPSO, an LNG RV, and an LNG FSRU.

According to another aspect of the invention, the step of controlling the cofferdam to a certain sub-zero temperature to reduce the BOR; Controlling the cofferdam to a specific temperature, including the temperature of the image, such that an operator enters the cofferdam controlled to a sub-zero temperature; And when the operator exits the cofferdam can be provided a temperature control method of the floating offshore structure comprising the step of controlling the cofferdam again to a specific temperature below zero.

The cofferdam can be controlled to a temperature range of -55 ~ 70 ℃.

According to another aspect of the present invention, by controlling the cofferdam provided between a plurality of LNG storage tank to a sub-zero temperature BOR (Boil) generated by heat transfer from the cofferdam to the interior of the plurality of LNG storage tanks A floating offshore structure may be provided, wherein the sub-zero temperature is reduced by heating the heating part provided in the hull and maintained at a specific temperature including the image temperature.

According to another aspect of the invention, the gas provided to the cofferdam provided between the plurality of LNG storage tank to be controlled to sub-zero temperature, the dew point temperature of the gas is lower than the temperature of the bulkhead of the cofferdam Floating offshore structure can be provided.

According to another aspect of the present invention, by controlling a cofferdam provided between a plurality of LNG storage tanks installed in one row or more in the longitudinal direction of the hull to sub-zero temperatures from the cofferdam to the plurality of LNG storage tanks Floating offshore structure can be provided that reduces the Boil-off Rate (BOR) generated by heat transfer to the interior of the.

According to another aspect of the present invention, by controlling a cofferdam provided between a plurality of LNG storage tanks installed in one row or more in the longitudinal direction of the hull to sub-zero temperatures from the cofferdam to the plurality of LNG storage tanks A floating offshore structure may be provided that reduces the BOR (Boil-off Rate) generated by heat transfer to the inside of the cofferdam, wherein the insulation is provided at the cofferdam.

According to another aspect of the invention, a floating offshore structure may be provided, characterized in that the insulation is installed in the cofferdam provided between the plurality of LNG storage tanks installed in one or more rows in the longitudinal direction of the hull. .

According to another aspect of the invention, the bulk head is provided between the plurality of LNG storage tanks connected to only the inner hull without extending to the outer hull, the bulk member is a strength member for connecting the outer hull and the inner hull Floating offshore structures may be provided so as not to be continuous with the head to reduce a Boil-off Rate (BOR) generated by heat transfer from the bulk head to the interior of the plurality of LNG storage tanks.

According to another aspect of the present invention, the bulk head for partitioning a plurality of LNG storage tanks are made of cryogenic material, but a pair of bulk heads are spaced apart from the foremost front and stern rear to provide a space, but the LNG storage tank and Floating offshore structure, characterized in that the insulating material is provided in the space portion other than the contacting bulk head may be provided.

Embodiments of the present invention can reduce the BOR (Boil-off Rate) generated by heat transfer between the cofferdam and the LNG stored in the plurality of LNG storage tanks by controlling the temperature of the cofferdam.

That is, the present embodiments do not reduce the BOR due to the deformation of the complicated and expensive LNG cargo hold, but reduce the BOR while maintaining the LNG cargo transport efficiency because the thermal inflow into the LNG cargo hold is reduced by reducing the temperature around the LNG cargo hold. You can.

In addition, in some embodiments of the present invention, when less BOG occurs, the control temperature is increased to generate more BOG, and when more BOG occurs, the control temperature is lowered so that less BOG can be adjusted. If the operator needs to enter the interior of the cofferdam to inspect the interior, the cofferdam can be controlled to the temperature of the image to allow the worker to enter the cofferdam.

1 is a side view schematically showing a state in which a cofferdam is installed in a floating offshore structure according to a first embodiment of the present invention.

FIG. 2 is a cross-sectional view taken along the line II-II of FIG. 1.

3 is a cross-sectional view taken along line III-III of FIG. 1.

4 is a plan sectional view showing a cofferdam provided between two LNG storage tanks arranged in two rows in the floating offshore structure shown in FIG.

5 is a cross-sectional view taken along line IV-IV of FIG. 4.

6 is a table showing steel grades defined by IGC.

7 is a table showing a calculation result of the BOR generated by the temperature control of the cofferdam in the first embodiment of the present invention.

FIG. 8 is a view schematically showing a state in which a heating unit is provided in a floating offshore structure in the first embodiment of the present invention.

FIG. 9 is a view schematically illustrating a state in which insulation is provided in a cofferdam in an insulation system of a floating offshore structure according to a second embodiment of the present invention.

FIG. 10 is a perspective view schematically illustrating a state in which a heat insulating material is provided in region “A” of FIG. 9.

FIG. 11 is a perspective view schematically illustrating a state in which a heat insulating material is provided in region “B” of FIG. 9.

FIG. 12 is a view schematically illustrating a heat insulating material damage preventing member provided to prevent damage of the heat insulating material in the region “C” of FIG. 10.

FIG. 13 is a table showing a calculation result of BOR generated by controlling the temperature of the cofferdam by the heat insulating material shown in FIG. 9.

14 is a view schematically showing a state in which the bulkhead of the cofferdam is connected only to the inner hull without extending to the outer hull in the floating offshore structure according to the third embodiment of the present invention.

15 is a modified embodiment of FIG. 14 in which a cofferdam is provided in place of the bulkhead shown in FIG. 14, and a heat insulating material is provided in the cofferdam.

FIG. 16 is a table illustrating a calculation result of BOR generated by manufacturing the bulk head of FIG. 13 from a cryogenic material and controlling the temperature of the cofferdam.

17 is a view schematically showing a gas supply unit in a floating offshore structure according to a fourth embodiment of the present invention.

FIG. 18 is a table showing a calculation result of BOR generated by controlling the temperature of the cofferdam shown in FIG. 17.

FIG. 19 is a view schematically illustrating controlling a temperature of a cofferdam in accordance with a pressure change of an LNG storage tank in a floating offshore structure according to a fifth embodiment of the present invention.

20 is a view schematically illustrating a state in which insulation is provided in a trunk deck space and a side passage in an insulation system of a floating offshore structure according to a sixth embodiment of the present invention.

FIG. 21 is a table showing a calculation result of BOR generated by controlling the temperature of the inner hull in contact with the trunk deck space and the side passage shown in FIG. 20.

FIG. 22 is a view schematically illustrating a state in which a heat insulating material is provided in a ballast tank in a heat insulating system of a floating offshore structure according to a seventh embodiment of the present invention.

FIG. 23 is a table showing a calculation result of BOR generated by controlling the temperature of an internal hull in contact with a ballast tank. FIG.

<Short description of drawing symbols>

1,200,300,400: Floating offshore structures

100,500,600: Insulation system of floating offshore structures

10: copper dam 30: heating unit

120: heat insulating material 220: strength member

320: gas supply unit

In order to fully understand the present invention, the operational advantages of the present invention, and the objects achieved by the practice of the present invention, reference should be made to the accompanying drawings which illustrate preferred embodiments of the present invention and the contents described in the accompanying drawings.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. Like reference numerals in the drawings denote like elements.

In the present specification, the floating offshore structure is a concept including both a vessel and various structures used while floating in the sea while having a storage tank for storing LNG, LNG FPSO (Floating, Production, Storage and Offloading), LNG Floating Storage and Regasification Unit (FSRU), LNG Carrier, LNG Regasification Vessel (RV RV).

1 is a side view schematically illustrating a cofferdam installed in a floating offshore structure according to a first embodiment of the present invention, FIG. 2 is a cross-sectional view taken along line II-II of FIG. 1, and FIG. 3 is FIG. 4 is a cross-sectional view illustrating a state in which a cofferdam is provided between LNG storage tanks arranged in two rows in the floating offshore structure shown in FIG. 1, and FIG. 5 is a cross-sectional view of FIG. 6 is a cross-sectional view taken along line IV-IV of FIG. 6, and FIG. 6 is a table showing steel grades defined by IGC, and FIG. 7 is a diagram illustrating BOR generated by temperature control of a cofferdam in a first embodiment of the present invention. 8 is a table illustrating a calculation result, and FIG. 8 schematically illustrates a state in which a heating unit is provided in a floating offshore structure in the first embodiment of the present invention.

In this embodiment, the cofferdam 10 is controlled to a sub-zero temperature to reduce the BOR (Boil-off Rate) generated by heat transfer from the cofferdam 10 into the LNG storage tank T.

As shown in these figures, the floating offshore structure 1 according to the present embodiment is provided between a plurality of LNG storage tanks T installed in one or more rows in the longitudinal direction of the hull, but at subzero temperatures. It is provided with a cofferdam 10 to be controlled.

The cofferdam 10 is provided in a plurality of LNG storage tanks T installed in one or more rows in the longitudinal direction of the hull, and as shown in FIGS. 1 to 3, arranged in multiple rows in the longitudinal direction of the hull. It may be provided between the plurality of LNG storage tank (T), or as shown in Figure 4 and 5, may be provided between the LNG storage tank (T) arranged in two rows in the width direction and the longitudinal direction of the hull. .

In the present embodiment, the copper dam 10 is controlled to a temperature below zero unlike the conventional to reduce the Boil-off Rate (BOR).

Specifically, conventionally, the temperature of the cofferdam is always maintained at 5 ° C or higher, which means that the bulkhead of the cofferdam using steel grade A specified by IGC when the temperature of the cofferdam is controlled below 5 ° C. This is because the temperature of (11) is lower than 0 ° C., so that there is a risk of brittle fracture.

As described above, when the temperature of the cofferdam is maintained at 5 ° C or higher, BOR is generated due to heat transfer due to a temperature difference between the cofferdam and LNG stored in the LNG storage tank (T). As shown in the table of FIG. 6, a BOR of 0.1282 is calculated.

However, when the temperature of the cofferdam 10 is controlled to a sub-zero temperature as in the present embodiment, the temperature difference between the LNG and the cofferdam 10 is reduced, so that the heat transfer between the LNG and the cofferdam 10 is reduced as compared with the related art. It can be seen that this leads to a decrease in BOR.

Therefore, in the present invention, when the bulk head of the cofferdam is made of a material that can withstand at -30 ~ 0 ℃, the cofferdam can be varied in the range of -30 ~ 70 ℃, the bulk head of the cofferdam is -55 When made of low temperature steel (LT) that can withstand temperatures up to -55 ° C, specifically, below -31 ° C, the cofferdam may be altered in the range of -55 to 70 ° C.

Specifically, as shown in the table of FIG. 7, when the temperature of the bulkhead 11 of the cofferdam 10 is controlled to −25 ° C., the temperature of the cofferdam 10 may be maintained at −20.8 ° C., in this case The BOR is 0.1236, which can be seen that the number is reduced by 3.5% compared to the conventional BOR.

In addition, as shown in the table of FIG. 7, when the temperature of the bulkhead 11 of the cofferdam 10 is controlled at −50 ° C., the temperature of the cofferdam 10 may be maintained at −46.5 ° C., in which case BOR Is 0.1192, which is 7.0% lower than that of the conventional BOR. For reference, the numerical value of BOR described above is a result of numerical analysis.

However, when the temperature of the cofferdam 10 is maintained at a sub-zero temperature, the bulk head 11 must be made of a material prescribed by IGC or low temperature steel (LT), so it can be expected that the cost will be increased. Since the increase is small compared to the benefits of reducing the BOR, the BOR can be effectively reduced at a relatively low cost.

In addition, the loss of LNG evaporated to BOG due to the reduction in the BOR can be prevented, and thus the increase in the aforementioned costs can be sufficiently offset.

Now, the cofferdam 10 will be described in detail. In the present embodiment, the cofferdam 10 is a pair of bulkheads spaced apart from each other between the plurality of LNG storage tanks T, as shown in FIG. 1. And a space portion 12 provided by a pair of bulk heads 11 and an inner hull IH, and by controlling the pair of bulk heads 11 to a sub-zero temperature, a cofferdam ( The temperature of 10) can be controlled to minus zero.

In the present embodiment, the temperature of the cofferdam 10 is, for example, to adjust the set temperature at which the heating system of the cofferdam 10 operates, or to install or insulate the heat insulator 120 (see FIG. 9) in the cofferdam 10. Injected gas into the cofferdam 10 can be adjusted to sub-zero temperatures.

Specifically, when designing the LNG carrier, the LNG carrier should be designed so that there is no problem even when the outside air temperature is -18 ° C and the seawater temperature is 0 ° C according to USCG conditions. If the cofferdam 10 is not heated at such an external temperature condition, the cofferdam 10 is dropped to -60 ° C by cold heat of LNG stored in the LNG storage tank (T).

Therefore, conventionally, the cofferdam 10 is heated, and temperature is always controlled to 5 degreeC in the space part 12 of the cofferdam 10, and the bulk head 11 to 0 degreeC or more.

However, in the present embodiment, unlike the conventional LNG carriers, when the temperature below zero is proposed in this embodiment, the heating device is operated to adjust the temperature of the cofferdam 10 to a specific temperature below zero.

In addition, by installing a heat insulator 120 (see FIG. 9) inside the cofferdam 10, the cofferdam 10 can be controlled to a sub-zero temperature, and the heat insulator 120 will be described in detail in the second embodiment described later. Explain.

In the present embodiment, the above-described method of controlling the temperature of the cofferdam 10 to a sub-zero temperature may be used independently or may be used together with other methods, so the scope of the present invention is limited to applying any one method. It doesn't work.

Since the bulk head 11 of the copper dam 10 is controlled to sub-zero temperatures, the bulk head 11 is made of B, D, E, AH, DH, EH, which are steel grades prescribed by IGC. Can be.

In particular, when the bulk head 11 of the cofferdam 10 is controlled to -30 ~ -20 ℃, the bulk head 11 can be manufactured by E or EH, which is a steel grade prescribed by IGC, the bulk head 11 When it is controlled to -60 ~ -30 ℃ can be produced the bulk head 11 by low temperature steel (LT).

In the present embodiment, when the bulk head 11 is made of low temperature steel, the low temperature steel may be low temperature carbon steel, low temperature alloy steel, nickel steel, aluminum steel, or austenitic stainless steel. It may be made of one or more combinations of at least one of the steels.

1 and 3, when arranging the cofferdam 10 in one row in the width direction of the hull, the space part 12 includes a pair of bulkheads spaced apart in the longitudinal direction of the hull ( 11 may form the front wall 7a and the rear wall 9a, and the inner hull IH may form the left and right side walls, the ceiling and the bottom.

Furthermore, in the present embodiment, as shown in FIG. 4, the cofferdam 10 divides the internal space of the LNG storage tank T in the transverse direction and the cofferdam 10a in the longitudinal direction. It includes a longitudinal copper dam 10b.

In this case, in the space part 12 of the cofferdam 10, in the case of the lateral cofferdam 10a, a pair of bulk heads 11 spaced apart in the longitudinal direction of the hull, respectively, based on FIG. The front wall and the rear wall of (12) can be formed, the inner hull IH on the right side can form the right wall 3a, and the partition wall on the left side can form the left wall 5a, and the inner hull IH Ceiling walls and floor walls can be formed.

In addition, in the case of the longitudinal cofferdam 10b, a pair of bulk heads 11 spaced apart in the width direction of the hull can form the right side wall and the left side wall of the space part 12, respectively, based on FIG. The wall where the bulkhead 11 of the longitudinal cofferdam 10b and the bulkhead 11 of the lateral cofferdam 10a contact each other may form the front wall 7a and the rear wall 7b, The inner hull IH may form a ceiling wall and a bottom wall.

The space part 12 of the present embodiment may be provided with the heat insulating material 120 of the second embodiment, which will be described later, and the heat insulating material 120 will be described in detail in the second embodiment.

The gas supply unit supplies gas into the cofferdam 10 to prevent the cofferdam 10 from being damaged by frost or change in humidity of the cofferdam 10.

In the present embodiment, the gas supply unit may be configured in the same manner as the gas supply unit 300 (see FIG. 17) of the fourth embodiment to be described later, and the gas supplied from the gas supply line to the cofferdam 10 may be branched from the gas supply line. Supply pipes to be supplied to the inside of the pipe), discharge pipes provided in the cofferdam 10 to discharge gas filled in the cofferdam 10 to the outside of the cofferdam 10, and supply pipes and discharge pipes It includes a valve.

The supply pipe of the gas supply part may be provided in a number corresponding to the cofferdam 10, and the lower end of the supply pipe may be disposed to be close to the bottom of the cofferdam 10.

The discharge pipe of the gas supply part may be provided in a number corresponding to the cofferdam 10 to discharge the gas filled in the respective cofferdam 10, respectively, or may be connected to each other to be discharged.

The valve of the gas supply unit 20 may be a proportional control valve opened and closed by an electrical signal.

In this embodiment, the gas supplied to the gas supply line includes dry air, inert gas, or N2 gas, which is an existing dry air / inner already installed in the LNG carrier. It can be supplied from a gas generator.

Meanwhile, the present exemplary embodiment may include a heating unit 30 that controls the temperature of the cofferdam 10 dropped to the first sub-zero temperature to a second sub-zero temperature higher than the first temperature.

In the present embodiment, as shown in FIG. 8, as shown in FIG. 8, the clevis heating coil 31 is installed inside the cofferdam 10 and the clevis heated to the clevis heating coil 31 ( The bulk head 11 may be heated by supplying glycol, or an electric coil may be installed inside the cofferdam 10 to heat the bulk head 11.

In addition, the bulk head 11 may be heated by providing a coil through which waste heat of exhaust gas or high temperature liquid or steam may be circulated inside the cofferdam 10.

In the present embodiment, when the glycol is used as an antifreeze, 45% of glycol water having a freezing point of −30 ° C. may be used.

Referring to Figure 8 will be briefly described a method for heating the glycol supplied to the cofferdam (10).

The glycol circulated by the glycol circulation pump is heated by a high temperature steam supplied from a boiler or the like in the glycol heater GH before being supplied to the cofferdam 10, and the heated glycol is a glycol provided inside the cofferdam 10. It is supplied to the heating coil 31 and circulated after heating the bulk head 11.

In the present embodiment, the cofferdam 10 may be provided with a temperature sensor TS capable of measuring the temperature inside the cofferdam 10, and is heated when the temperature inside the cofferdam 10 is lower than a set value. The glycol may be supplied to the glycol heating coil 31 attached to the bulk head 11 to increase or maintain the temperature of the bulk head 11 and the space 12.

On the other hand, when the temperature of the bulk head 11 is controlled to -50 ° C or lower, since the freezing point of the antifreeze may drop below -50 ° C, the antifreeze may use glycol water 65% or methyl alcohol. Content described in the embodiment can be applied to other embodiments as described later.

FIG. 9 is a view schematically showing a state in which insulation is provided in a cofferdam in an insulation system of a floating offshore structure according to a second embodiment of the present invention, and FIG. 10 is a state in which insulation is provided in region “A” of FIG. 9. 11 is a perspective view schematically illustrating a state in which insulation is provided in region “B” of FIG. 9, and FIG. 12 is a modified embodiment of the insulation provided in region “C” of FIG. 10. FIG. 13 is a table showing a calculation result of BOR generated by controlling the temperature of the cofferdam by the heat insulating material shown in FIG. 9.

The thermal insulation system 100 of the floating marine structure according to the present embodiment controls the temperature of the cofferdam 10 to subzero temperature regardless of the spatial environment such as the polar region or the tropical region, or the temporal environment such as the season and the day / night. In order to provide a heat insulating material 120 provided in the cofferdam (10).

As shown in FIG. 9, the heat insulator 120 is provided in the cofferdam 10 to allow heat to penetrate into the cofferdam 10 when the floating offshore structure is operated in a high temperature region or in summer. It prevents the temperature of the cofferdam 10 to fall to the desired temperature even if the outside temperature is high.

Specifically, when the outside temperature is high, for example, when the temperature of the outside air presented in the IGC code is 45 ℃, seawater temperature is 25 ℃ when not installing the heat insulator 120, as shown in the table of FIG. Likewise, the temperature of the cofferdam 10 may only fall to -15.39 ° C., which may limit the reduction of BOR.

However, when the insulation 120 is provided in the cofferdam 10 as in the present embodiment, the cofferdam 10 is sufficiently lowered to a desired temperature, for example, -25 ° C or -50 ° C even under the above-described conditions. BOR reduction can be seen.

Now, the heat insulator 120 will be described in detail, in this embodiment, the heat insulator 120, in consideration of the convenience and cost of work, as well as the heat insulation wall used to insulate the LNG stored in the LNG storage tank (T). Other types than the above-described heat insulation walls can be used.

That is, in this embodiment, the heat insulating material 120 may include at least one of a panel type heat insulating material, a foam type heat insulating material, a vacuum heat insulating or particle type heat insulating material, and a non-woven heat insulating material different from the above-described heat insulating wall. have.

In this embodiment, the heat insulator 120 may be applied without limitation to the type and shape. In consideration of the working environment and cost, only one of the three types of heat insulating materials described above may be used, or two or more heat insulating materials may be selected and used. In addition, an insulating wall for insulating the LNG stored in the LNG storage tank (T) may be used. Here, the heat insulating wall refers to the heat insulating wall of the sealing and heat insulating unit (SI).

The panel type insulation includes styrofoam, and the styrofoam may be coupled to the cofferdam 10 by a low temperature adhesive or bolt.

Insulation of the foam type includes a polyurethane foam, the polyurethane foam may be sprayed to the copper dam 10 in a foaming (foaming) method to be combined.

Non-woven type insulation may be made of polyester fiber material, may be made of a synthetic resin layer, it may be coupled to the copper dam 10 by an adhesive method using a low temperature adhesive or bolts.

There is no restriction on the type and installation method of the heat insulating material 120 in the present invention.

In the present embodiment, as shown in FIG. 9, the heat insulating material 120 may be provided in the space portion 12 of the cofferdam 10 in the region excluding the pair of bulk heads 11.

Specifically, as shown in FIG. 10, in the case of the lateral cofferdam 10a, the heat insulating material 120 is provided at the right wall part, the left wall part, the ceiling part and the bottom part of the space part 12 of the cofferdam 10, respectively. Can be. In addition, the heat insulating material 120 provided at the ceiling and the bottom may be provided outside the space 12.

In this way, when the heat insulator 120 is provided in the cofferdam 10 in the region excluding the pair of bulk heads 11, the heat outside the region not in contact with the pair of bulk heads 11 is in the cofferdam 10. It is possible to prevent the intrusion into the interior of the, and the cold heat of the LNG stored in the LNG storage tank (T) through the pair of bulk head 11 can be transmitted to the space portion 12, the temperature outside the hull is high Even in this case, the temperature of the cofferdam 10 may be lowered to a desired temperature.

In addition, in the present embodiment, the heat insulator 120 is disposed in the foremost front bulkhead 11 and the stern rear of the transverse cofferdam 10a disposed at the foremost front of the plurality of cross cofferdams 10a. The stern rearward bulkhead 11 of the cofferdam 10a may be provided respectively.

Specifically, FIG. 11 illustrates that the insulator 120 is provided on the bulkhead 11 at the forefront of the bow, and the forefront and the stern rear of the bow have different environments from the area between the bow and the stern.

That is, since the LNG storage tank (T) is in contact with only one direction and the inner wall of the hull, the forefront and stern rear regions are in the region between the bow and the stern to lower the temperature of the cofferdam (10) to the desired temperature. It is more difficult than the copper dam 10.

However, if the insulation 120 is also provided to the foremost bulkhead 11 and the foremost rear bulkhead 11 as in the present embodiment, it is possible to prevent external thermal intrusion, thereby lowering the cofferdam 10 to a desired temperature. Can be.

On the other hand, when the heat insulating material 120 is installed inside the cofferdam 10, the heat insulating material 120 provided in the bottom of the cofferdam 10 may be damaged by the source. That is, when the worker enters the inside of the cofferdam 10, the bottom of the cofferdam 10 should be supported by the foot, and the heat insulating material 120 may be damaged.

Therefore, in this embodiment, in order to prevent the damage of the above-described heat insulating material 120, as shown in Figure 12, it is possible to provide a heat insulating material damage preventing member.

In this embodiment, the heat insulating material damage preventing member 130a, as shown in (a) of Figure 12, is provided in a grid form (grid) is disposed on the heat insulating material 120, the load is applied to a specific portion of the heat insulating material 120 By preventing concentration, damage to the heat insulating material 120 may be prevented.

In addition, the insulation damage preventing member 130b may be a separate path provided at the bottom of the cofferdam 10 so that the source can move to a desired place. Since the area mainly approached by the source is the edge of the bottom portion, the heat insulating material damage prevention member (130b), as shown in Figure 12 (b), will be provided with a slight width only on the bottom edge of the cofferdam (10). Can be.

Figure 13 shows the effect of reducing the BOR by the installation of the insulation and the temperature control of the cofferdam.

As in the prior art, if the cofferdam is controlled at 5 ° C., the BOR is about 0.1282. Here, even if the temperature of the glycol heating system is controlled to control the temperature of the cofferdam, the cofferdam may not drop to only -10.87 ° C even at the lowest temperature when the glycol heating is not performed.

Therefore, even if the bulkhead 11 of the cofferdam is made of steel grade E, which can be applied up to -25 ° C, the temperature of the cofferdam only falls to -15.39 ° C, which reduces BOR only by about 2.2%.

However, by applying the present embodiment by installing the heat insulator 120 so that the cofferdam 10 falls to -26.4 ℃, and control by raising the temperature to -20.8 ℃ by glycol heating can reduce the BOR by about 3.5.

The contents of the first embodiment described above can be applied to the present embodiment as it is.

14 is a view schematically showing a state in which the bulkhead of the cofferdam is connected only to the inner hull without extending to the outer hull in the floating offshore structure according to the third embodiment of the present invention, and the bulk shown in FIG. 14 is a modified embodiment of FIG. 14 in which a cofferdam is provided instead of a head, and a heat insulating material is provided in the cofferdam, and FIG. 16 is a calculation of BOR generated by fabricating the bulkhead shown in FIG. 13 using a cryogenic material and controlling the temperature of the cofferdam. The table shows the results.

The thermal insulation system 200 of the floating offshore structure according to the present embodiment is provided between the plurality of LNG storage tanks T to provide the plurality of LNG storage tanks T at least one of the longitudinal direction and the width direction of the hull. The bulk head 210 is arranged in a row in a direction but is not extended to the outer hull EH and is connected only to the inner hull IH, and the inner hull IH and the outer hull EH are connected to reinforce both, but the bulk head ( The strength member 220 which is not continuous with 210, the heat insulating material 120 provided in the foremost front and the stern rear, and the space part 12 provided by the bulk head 210 in the foremost front and the stern rear, the gas It includes a gas supply unit 20 for supplying the gas to prevent the space is damaged by the change in humidity, and the heating unit 30 for heating the bulk head 210 provided in the foremost front and the stern rear.

As shown in FIG. 14, the bulk head 210 may arrange the LNG storage tanks T in a row in the longitudinal direction of the hull or in a row in the width direction of the hull.

In addition, since the sealing and insulating unit (SI) and the heat insulating material 120 is not provided in the area where the bulk head 210 and the LNG storage tank (T) contact in the present embodiment, the bulk head 210 is a cryogenic temperature of -140 ℃ The temperature can drop.

Therefore, in the present embodiment, the bulk head 210 may be made of a cryogenic material including stainless steel or aluminum, and the end of the sealing wall of the sealing and insulating unit (SI) for sealing and insulating the LNG storage tank (T). May be directly welded to the bulk head 210.

In addition, the bulk head 210 of the present embodiment may be provided with a pair of spaced apart from the foremost and the rear of the stern, the space portion 12 in the forefront and the foremost of the stern. The bulk head 210 of the space part 12 may be provided with a heat insulating material 120 and a heating part 30, and the space part 12 may be provided with a gas supply part to prevent damage to the bulk head 210. Gas can be supplied.

On the other hand, the bulk head 210 of the present embodiment, unlike the prior art, as shown in Figure 14, does not extend to the outer hull (EH). This is because when the bulk head 210 is connected to the outer hull EH, external heat may be transferred through the bulk head 210 to increase the BOR, and the outer hull EH is in contact with the bulk head 210. This is because brittle fracture may be caused by cold heat transmitted from the bulk head 210.

The strength member 220, as shown in Figure 14, serves to structurally reinforce the hull by connecting the inner hull (IH) and the outer hull (EH) at an intermediate position of the LNG storage tank (T).

The strength member 220 of the present embodiment, as shown in Figure 14, is provided so as not to be continuous with the bulk head 210, the cold heat transmitted through the bulk head 210 is provided at both ends of the bulk head 210 It can be offset by the sealing and insulation unit (SI), it can be seen that the heat transfer from the outside is also reduced because the bulk head 210 is not in direct contact with the outer hull (EH).

The strength member 220 of the present embodiment may be provided at any position where the bulk head 210 is not continuous, and the number thereof is not limited.

In addition, since the strength member 220 is not exposed to cryogenic temperatures, the strength member 220 may be made of steel of steel grade A.

As the heat insulator 120, the heat insulator 120 of the above-described second embodiment may be applied as it is. However, there is a difference in that the installation position is provided at the forefront and the stern rear, not between the LNG storage tank (T).

The gas supply unit and the heating unit 30 may be applied to the first embodiment as described above. However, there is a difference from the above-described first embodiment in that it is applied to the space 12 provided at the foremost front and the stern rear.

In this embodiment, the bulkhead 210, not the cofferdam 10, is provided between the LNG storage tanks T to directly control the temperature of the bulkhead 210 disposed between the LNG storage tanks T. Since it is not easy, the above-described bulk head 210 is controlled to about -130 ℃ due to the direct contact of the LNG.

However, the bulk head 210 disposed at the foremost front and rear of the stern can be freely controlled by the heating unit 30, and the bulk head 210 is disposed between the LNG storage tanks T. In this case, the temperature of the bulkhead 210 may be controlled by adjusting the insulation wall of the sealing and insulating unit SI or by heating both ends of the bulkhead 210 with an electric coil.

In addition, in the present embodiment, as shown in FIG. 15, two or more bulkheads 210 may be provided, two or more bulkheads 210 may be arranged to be spaced apart from each other, and the inner hull IH may be provided. It is also applicable to the double hull structure consisting of) and the outer hull (EH).

On the other hand, this embodiment, as shown in Figure 14 and 15, may not provide a sealing and heat insulation unit (SI) in the area where the bulk head 11 and the LNG storage tank (T) contacted, in this case If the bulk head 11 is made of a cryogenic material and the temperature of the cofferdam 10 is controlled to a sub-zero temperature, a BOR as shown in FIG. 16 can be obtained.

Specifically, as shown in FIG. 14, when the sealing and insulating unit SI is not provided in the area where the bulk head 11 and the LNG storage tank T are in contact with each other, cold heat of LNG stored in the LNG storage tank T may be reduced. It is well transmitted to the cofferdam 10 so that the temperature of the cofferdam 10 can drop to −125 ° C., as shown in FIG. 16. At this time, it can be seen that BOR is 0.1061, which is 17.2% reduced than when the cofferdam 10 is controlled at 5 ° C.

In this case, the bulk head 11 of the cofferdam 10 may be controlled to a temperature of -163 ~ -50 ℃, the bulk head 11 is a cryogenic material containing stainless steel or aluminum, not the general material The sealing wall of the sealing and insulating unit (SI) in contact with the bulk head 11 may be coupled to the bulk head 11 in a welded manner.

FIG. 17 is a view schematically illustrating a gas supply unit in a floating offshore structure according to a fourth embodiment of the present invention, and FIG. 18 illustrates a calculation result of BOR generated by controlling a temperature of a cofferdam shown in FIG. 17. Table.

The floating offshore structure 300 according to the present embodiment is provided between the plurality of LNG storage tanks T and the plurality of LNG storage tanks T are arranged in at least one of the longitudinal direction and the width direction of the hull. A cofferdam 10 disposed at a subzero temperature, a gas supply unit 320 for supplying gas to the cofferdam 10, and a cofferdam 10 provided to a worker to the inner space of the cofferdam 10. It is provided with a heating unit 30 for heating the cofferdam 10 to enter, and the heat insulating material 120 provided in the cofferdam 10.

This embodiment has a gas supply unit 320 for supplying gas into the interior of the cofferdam 10 to easily find the cold spot formed in the bulk head 11 of the cofferdam 10 There is a difference from the first and second embodiments described above. The copper dam 10, the heating unit 30, and the heat insulating material 120 described in the above-described first and second embodiments may be applied as it is in the present embodiment.

In the floating offshore structure according to the present embodiment, an operator must periodically enter the cofferdam 10 to examine whether the bulkhead 11 of the cofferdam 10 has no cold spots. That is, it is necessary to check whether a cold portion occurs in a specific portion of the bulkhead 11 of the cofferdam 10, which can be seen that the frost is caught in the bulkhead 11 and is visually inspected.

However, if the temperature of the cofferdam 10 is maintained at a sub-zero temperature and the inside of the cofferdam 10 is filled with the general air, the frost is stuck to the entire bulkhead 11 of the cofferdam 10, the presence or absence of the castle Can not find cold spots.

Therefore, in the present embodiment, a gas, for example, dry air, is filled in the cofferdam 10 and the temperature of the bulk head 11 of the cofferdam 10 is controlled to be higher than the dew point of the dry air. This makes it easy to find the cold spot by causing frost only in the bulk head 11 lower than the dew point of the dry air.

For example, when the dew point temperature of the dry air generated in the LNG carrier is -40 ° C, the temperature of the bulkhead 11 of the cofferdam 10 is controlled to -35 ° C and visually enters into the cofferdam 10. When the bulkhead 11 of the cofferdam 10 lower than -40 ℃ because the frost is caught, it is easy to find the cold spot to the position of the frost.

In addition, the technical means for supplying dry air having a low dew point temperature to the inside of the cofferdam 10 may include a side in contact with the trunk deck space TS (see FIG. 21) and the trunk deck TD in the sixth embodiment described later. The same may be applied to the passage SP (see FIG. 21).

In addition, when the temperature of the bulkhead 11 of the cofferdam 10 is controlled to -35 ° C, as shown in the table of FIG. 18, the BOR can be reduced by about 4.9% compared to the control at 5 ° C. In this case, the bulk head 11 may be made of low temperature steel (LT).

In the present embodiment, as shown in FIG. 17, the gas supply unit 320 is provided in the cofferdam 10 to supply gas supplied through the gas supply line AL to the inside of the cofferdam 10. A pipe 321, a gas discharge pipe 322 provided in the cofferdam 10 to discharge the internal gas of the cofferdam 10 to the outside of the cofferdam 10, a gas supply pipe 321, and a gas discharge pipe On and off valve 323 is provided in the (322).

In this embodiment, the dry air supplied to the gas supply line AL may be supplied from a dry air generator installed in an existing LNG carrier so that no additional cost for this facility is incurred.

In this embodiment, the dry air supplied to the cofferdam 10 may have a dew point temperature of -45 ~ -35 ℃, the temperature of the bulk head 11 of the cofferdam 10 is 1 than the dew point temperature of the dry air Can be controlled as high as ~ 10 ℃. In this case, since the temperature of the bulk head 11 is controlled at about -30 ° C, the BOR can be reduced.

When personnel have to enter the cofferdam 10 due to inspection and maintenance reasons, it is possible to prevent work at low temperatures by performing clothes such as winter clothes. On the other hand, by continuously injecting and venting the above-described gas into the cofferdam 10 has the advantage that the personnel can enter the work by raising the temperature of the cofferdam.

FIG. 19 is a view schematically illustrating controlling a temperature of a cofferdam in accordance with a pressure change of an LNG storage tank in a floating offshore structure according to a fifth embodiment of the present invention.

The thermal insulation system 400 of the floating offshore structure according to the present embodiment is provided between the plurality of LNG storage tanks T to form a plurality of LNG storage tanks T in at least one of the longitudinal direction and the width direction of the hull. And a heating unit 30 arranged in the cofferdam 10 to heat the cofferdam 10, the cofferdam 10 being arranged in multiple rows and controlled at a sub-zero temperature, and the sub-zero temperature of the cofferdam 10. Is different from the first embodiment in that it is controlled by the temperature of the heating furnace 30, the temperature of the cofferdam 10 in accordance with the change in the internal pressure of the LNG storage tank (T). The contents of the remaining first embodiment can be applied to the present embodiment as it is.

In other words, the present embodiment not only maintains the temperature of the cofferdam 10 to sub-zero temperatures to lower the BOR, but also requires a little more BOG depending on the sailing conditions, so that more BOG is needed for reasons such as ship fuel. Increase the temperature of 10) to increase the BOR so that more BOG is generated, and if the BOG is difficult to process due to too many BOGs depending on the sailing conditions, lower the temperature of the cofferdam 10 to make BOR smaller. You can get a little more BOG.

The above-described control temperature may be set manually in consideration of sailing conditions or the like, or may be automatically controlled by receiving a pressure signal from the LNG storage tank T. In other words, if the pressure in the LNG storage tank (T) is high, the BOG is excessively generated. Therefore, the control temperature is controlled to be lowered. If the pressure is low, the BOG is slightly generated. Can be controlled.

In addition, the present embodiment not only maintains the temperature of the cofferdam 10 to the sub-zero temperature to lower the BOR, but also the temperature of the cofferdam 10 so that an operator can enter the inside of the cofferdam 10 to a specific temperature (eg , The temperature of the image) is different from the above-described first embodiment.

In detail, the operator needs to enter the inside of the cofferdam 10 to check whether a cold spot or the like has occurred in the cofferdam 10 during operation.

At this time, if the cofferdam 10 is maintained at a sub-zero temperature, the worker entering the cofferdam 10 may be exposed to a low temperature, which may be dangerous. Therefore, the cofferdam may be raised to the heating unit 30 by raising the set value of the control temperature. The cofferdam 10 may be maintained at a specific temperature (eg, the temperature of the image) by heating the 10.

In the present embodiment, when the bulk head 11 of the cofferdam 10 is made of a material that can withstand -30 to 0 ° C, the temperature of the cofferdam 10 may be controlled in the range of -30 to 70 ° C. For example, if the worker does not need to enter the inside of the cofferdam 10, the control temperature of the cofferdam 10 can be controlled to about -30 ℃ to reduce the BOR as much as possible, and vice versa 10) can be controlled to a specific temperature including the temperature of the image.

In the present embodiment, when the bulk head 11 of the cofferdam 10 is made of low temperature steel LT that can withstand up to -55 ° C, the temperature of the cofferdam 10 is controlled in the range of -55 to 70 ° C. can do. For example, if the worker does not need to enter the inside of the cofferdam 10, the temperature of the cofferdam 10 can be controlled to about -50 ℃ in order to reduce the BOR as much as possible, and vice versa ) Can be controlled to a specific temperature, including the temperature of the image.

Hereinafter, a method of controlling a temperature of the cofferdam in order for an operator to enter the inside of the cofferdam 10 will be described.

First, the temperature of the cofferdam 10 is controlled to a sub-zero temperature, for example, -25 ℃ or -50 ℃ to reduce the heat transfer between the copper dam 10 and the LNG stored in the LNG storage tank (T) Getting inside the cofferdam can be dangerous.

Therefore, a step of heating the cofferdam 10 to the temperature of the image by the heating unit 30 is made. In this case, the cofferdam 10 may be heated by a glycol heating coil 31, an electric coil, steam, or a coil through which fresh water flows, or may be heated by supplying hot air into the cofferdam 30.

Next, when the internal temperature of the cofferdam 10 is the temperature of the image, the operator enters and checks whether a cold spot or the like has occurred in the bulk head 11. At this time, the inside of the cofferdam 10 is continuously maintained at the temperature of the image.

When the worker completes the internal inspection of the cofferdam 10 and comes out of the cofferdam 10, the heating of the cofferdam 10 is stopped to maintain the cofferdam 10 at a temperature below zero.

As described above, in the present embodiment, when the worker does not need to enter the inside of the cofferdam 10, the cofferdam 10 may be maintained at a sub-zero temperature to reduce the BOR, and vice versa. ) Can be considered as operator's safety while reducing the BOR.

For the technical means for controlling the temperature of the cofferdam 10 described above, the trunk deck space TS (see FIG. 21) and the side passages SP and FIG. 21 in contact with the trunk deck TD are described in the sixth embodiment described later. ) Can be applied as is.

In addition, the present embodiment is different from the above-described first embodiment in that the temperature of the cofferdam 10 can be controlled according to the change in the internal pressure of the LNG storage tank (T).

Specifically, in the present embodiment, as shown in FIG. 19, the pressure sensor PT capable of measuring the internal pressure of the LNG storage tank T is provided in the LNG storage tank T, and then the pressure sensor PT. The temperature of the cofferdam 10 can be controlled based on the pressure measured at.

In other words, when the pressure of the LNG storage tank (T) increases, more BOG is generated than the BOG required for the floating offshore structure, and thus the cofferdam (10) is lowered by lowering the setting temperature of the cofferdam (10) temperature control. Lowering the temperature of) can cause the BOG to decrease. When the pressure of the LNG storage tank (T) is lowered, less BOG is generated than the BOG required for the floating offshore structure. Therefore, the temperature of the cofferdam 10 is increased by increasing the setting temperature of the cofferdam 10 temperature control. More BOG can be generated.

In addition, the temperature of the cofferdam 10 may be controlled by referring to the speed of the floating offshore structure regardless of the pressure sensor PT.

Specifically, if the fuel consumption is large due to the high speed of the floating offshore structure, the control temperature of the cofferdam 10 may be increased to generate more BOG, and the generated BOG may be used as fuel to match the fuel consumption.

For example, a floating offshore structure that controls the bulkhead 11 of the cofferdam 10 to a set temperature of -25 ° C has a BOR of 0.1236. When the floating offshore structure is to increase the speed and consume more fuel, if the temperature of the cofferdam 10 bulkhead 11 is controlled at 0 ° C., the BOR is increased by 3.7% and 3.7% to increase the BOG. As a result, the speed of the floating offshore structure is increased to reduce the amount of BOG that is insufficient when the consumption of BOG increases.

On the contrary, when the speed of the floating offshore structure is low and the fuel consumption is low, the fuel consumption may be adjusted by lowering the control temperature of the cofferdam 10 to generate a little BOG.

On the other hand, in the case of heating the bulk head 11 of the cofferdam 10 by the heating unit 30, since the heat transfer by conduction may take a heating time of the cofferdam 10, the inside of the cofferdam 10 The heating time of the cofferdam 10 may be shortened by supplying warm dry air.

In addition, the gas supply unit and the gas supply unit 320 described in the above-described embodiment may also be applied to the present embodiment.

FIG. 20 is a view schematically illustrating a state in which insulation is provided in a trunk deck space TS and a side passage in an insulation system of a floating offshore structure according to a sixth embodiment of the present invention, and FIG. 21 is illustrated in FIG. 20. It is a table showing the calculation result of BOR generated by controlling the temperature of the trunk hull space TS and the inner hull IH in contact with the side passages.

The insulation system 500 of the floating offshore structure according to the present embodiment is provided in at least one of a trunk deck space (TStrunk deck space) and a side passage (SP, side passage way) in contact with the trunk deck (Trunk deck (TD)) It is provided with a heat insulator 120 to reduce the heat cut from the trunk deck space (TS) or side passage (SP) to the interior of the plurality of LNG storage tank (T) to reduce the Boil-off Rate (BOR) generated by heat transfer do.

In the present embodiment, by reducing the temperature of the inner hull IH in contact with the trunk deck space TS and the side passage SP, the BOR can be reduced by reducing the amount of heat intrusion from the outside.

In particular, in the case of operating a low-temperature route, such as the Arctic route, or winter operation, the present embodiment lowers the temperature of the inner hull (IH) in contact with the trunk deck space (TS) and the side passage (SP). This can reduce the BOR.

On the contrary, when sailing to a place where the temperature is high or sailing in the summer, the copper dam 10 is lowered by lowering the temperature of the inner hull IH in contact with the trunk deck space TS and the side passage SP by the heat insulator 120. The temperature of the can be maintained at a low temperature to reduce the BOR.

In particular, since the trunk deck (TD) and the side passage (SP) in contact with the trunk deck (TD) is a place directly exposed to the sun's heat from the outside, providing a heat insulator 210 in this part can reduce the external heat intrusion to reduce the BOR Can be reduced more effectively.

As a result of calculating the BOR numerically for the actual LNG carrier, as shown in the table of FIG. 21, when the temperature of the inner hull IH in contact with the trunk deck space TS and the side passage SP is not controlled. The temperature of the inner hull (IH) is about 35.3 ℃, the BOR is calculated to be 0.1346.

However, when the temperature of the inner hull IH in contact with the trunk deck space TS and the side passage SP is controlled to 0 ° C. by applying the present embodiment, the BOR is 0.1296 as shown in the table of FIG. 21. As a result it was confirmed that the decrease of about 3.7%. It can be seen that the BOR can be reduced by using the insulator 120 having a low cost, and the BOR reduction effect for the price is large.

As another example, when the temperature of the inner hull IH in contact with the trunk deck space TS and the side passage SP is controlled to -25 ° C., the BOR decreases by about 5.9% to 0.1266. there was. In addition, it can be seen that the cost-effectiveness BOR reduction effect when using the low-cost insulation 120.

As shown in FIG. 20, the heat insulating material 120 includes an inner ceiling of the trunk deck TD, a ceiling and sidewalls of the side passage SP in contact with the trunk deck TD, and a side passage in contact with the ballast tank BT. (SP) can be provided in the part.

In the present embodiment, the heat insulating material 20 is not limited to the position of the trunk deck TD described above, but may be installed on the bottom or the outer portion of the trunk deck TD, and the trunk deck space TS and the side passage SP. It may be provided intermittently or continuously.

In addition, in this embodiment, the heat insulating material 120 of the above-described embodiment may be applied as it is. That is, the heat insulating material 120 of the present embodiment may be a heat insulating wall of a sealing and heat insulating unit (SI) for sealing and insulating the LNG storage tank (T), and a panel type heat insulating material and a heat insulating material of a foam type that are different from the heat insulating wall. It may include at least one of a vacuum insulation or a particle-shaped insulation and a nonwoven insulation. Furthermore, this invention does not have a restriction | limiting about the kind, form, and installation method of a heat insulating material.

The present embodiment may include a heating unit 30 for heating the inner hum IH to heat the cofferdam 10 or to maintain the inner hull IH at a desired temperature. The configuration of the heating unit 30 may include the glycol heating coil 31 of the above-described embodiment, an electric coil, a coil through which a liquid such as steam or fresh water flows, and the like.

In this embodiment, the material and temperature control of the inner hull IH in contact with the trunk deck space TS and the side passages SP may be selectively performed according to the required BOR value.

Specifically, in the present embodiment, the inner hull (IH) can be controlled to a temperature of -55 ~ 30 ℃, preferably, to be able to use the material of the inner hull (IH) as steel grade A prescribed by IGC It may be controlled to a temperature of 0 ~ 30 ℃. For example, when the temperature of the inner hull IH is controlled to 0 ° C., as shown in the table of FIG. 21, the BOR is reduced by 3.7% compared to the conventional embodiment in which the inner hull IH is controlled to 35.3 ° C. 0.1296 can be obtained and steel grade A can also be used for the inner hull (IH).

In addition, by controlling the temperature of the inner hull (IH) to -25 ° C, as shown in the table of Figure 21, it is possible to obtain 0.1266 with a 5.9% reduction in the BOR, the inner hull (IH) can use the steel grade E or EH Can be. In addition, when the temperature of the inner hull (IH) is controlled to -30 ° C or less, the inner hull (IH) can be made of low temperature steel (LT).

Meanwhile, in the present embodiment, the contents of the cofferdam 10, the gas supply part 320, and the gas supply part of the above-described embodiment may be applied as it is.

FIG. 22 is a view schematically showing a state in which a heat insulating material is provided in a ballast tank in a heat insulation system of a floating offshore structure according to a seventh embodiment of the present invention, and FIG. 23 shows a temperature of an inner hull IH in contact with a ballast tank. This table shows the calculation result of BOR generated by controlling.

The insulation system 600 of the floating offshore structure according to the present embodiment is provided in the ballast tank BT to reduce the heat transfer from the ballast tank BT to the inside of the LNG storage tank T to reduce the BOR ( 120).

In this embodiment, by lowering the temperature of the inner hull (IH) in contact with the LNG storage tank (T) in the ballast tank (BT) can reduce the amount of heat intrusion from the outside to lower the BOR.

Even when sailing to a high temperature or sailing in summer, the BOR can be reduced by lowering the temperature of the inner hull (IH) in contact with the LNG storage tank (T) in the ballast tank (BT) by the heat insulating material (120).

Specifically, in the present embodiment, the ballast tank BT and the LNG storage tank inner hull IH may be controlled at a temperature of −55 to 30 ° C. Preferably, the material of the inner hull IH is IGC. It can be controlled at temperatures between 0 and 20 ° C in order to be able to use steel grade A as specified in

As a result of calculating the BOR by numerical analysis on the actual LNG carrier, when the temperature of the inner hull IH in contact with the LNG storage tank T in the ballast tank BT is not controlled, as shown in the table of FIG. 23. , The temperature of this part is about 27.2 ~ 36.13 ℃, BOR is calculated as 0.1346.

However, in the case of controlling the temperature of the inner hull IH in contact with the LNG storage tank T at 0 ° C. in the ballast tank BT by applying the present embodiment, the BOR is 0.1242, as shown in the table of FIG. 23. It can be seen that the decrease of about 7.7%. That is, it can be seen that the BOR reduction effect of the price ratio is large because the BOR can be reduced at a cost of the insulator 120 of low cost.

In another example, when the temperature of the inner hull (IH) in contact with the LNG storage tank (T) in the ballast tank (BT) at 5 ° C it can be seen that the BOR is reduced by about 6.2% to 0.1262. In addition, it can be seen that the cost-effectiveness BOR reduction effect when using the low-cost insulation 120.

As illustrated in FIG. 22, the heat insulator 120 may be provided on the ceiling wall of the ballast tank BT in an area where the inner hull EH and the ballast tank BT and the site passage contact each other.

In addition, in this embodiment, the heat insulating material 120 of the above-described embodiment may be applied as it is. That is, the heat insulating material 120 of the present embodiment may be a heat insulating wall of a sealing and heat insulating unit (SI) for sealing and insulating the LNG storage tank (T), and a panel type heat insulating material and a foam type of a different type from the heat insulating wall. It may include at least one of a heat insulator, a vacuum heat insulator or a particle type insulator, and a nonwoven fabric insulator. Furthermore, the present invention is not limited to the type, form and installation method of the heat insulator.

The present embodiment may include a heating part 30 for heating the cofferdam 10 or heating the inner hull IH to maintain the inner hull IH in contact with the ballast tank BT at a desired temperature. The configuration of the heating unit 30 may include the glycol heating coil 31 of the above-described embodiment, the electric coil, a fluid coil through which steam or fresh water flows, and the like.

In the present embodiment, the material and temperature control of the inner hull IH in contact with the ballast tank BT may be selectively performed according to the required BOR value.

Specifically, in the present embodiment, the inner hull IH in contact with the ballast tank BT may be controlled at a temperature of -55 to 30 ° C. When the temperature of the inner hull IH is controlled to 0 ° C., as shown in the table of FIG. 23, the BOR decreases by 7.7% to 0.1242 compared to the conventional embodiment in which the inner hull IH is controlled to 27.1 to 36.1 ° C. Steel grade A can also be used.

In addition, if the temperature of the inner hull IH is controlled to 5 ° C., as shown in the table of FIG. 23, the BOR is reduced by 6.2% to 0.1262, and the inner hull IH may use steel grade A. .

Meanwhile, in the present embodiment, the contents of the cofferdam 10 and the gas supply part 320 of the above-described embodiment may be applied as it is. However, the gas supply unit 320 may not be applied when the ballast water is filled in the ballast tank BT, and thus may be applied only to the cofferdam 10.

As described above, the present invention is not limited to the described embodiments, and various modifications and changes can be made without departing from the spirit and scope of the present invention, which will be apparent to those skilled in the art. Therefore, such modifications or variations will have to be belong to the claims of the present invention.

Claims (25)

1. It includes a cofferdam provided between a plurality of LNG storage tanks installed in one row or more in the longitudinal direction of the hull,

   The cofferdam is controlled to a sub-zero temperature, the floating offshore structure characterized in that to reduce the Boil-off Rate (BOR) generated by heat transfer from the cofferdam to the interior of the plurality of LNG storage tanks.
2. The method according to claim 1,

   The cofferdam is,

   A pair of bulk heads spaced apart from each other between the plurality of LNG storage tanks; And

   It includes a space portion provided by the pair of bulk heads and the inner wall of the hull,

   Floating offshore structure, characterized in that for controlling the pair of bulk heads to sub-zero temperatures.
3. The method according to claim 2,

   The pair of bulk heads is a floating offshore structure, characterized in that made of one or more of the steel grade (steel grade) B, D, E, AH, DH and EH prescribed by IGC.
4. The method according to claim 1,

   And a gas supply unit supplying gas into the cofferdam to prevent the inside of the cofferdam from being damaged by freezing of moisture in the air.
5. The method according to claim 4,

   The gas supply unit,

   A supply pipe provided in the hull to supply the gas into the cofferdam;

   A discharge pipe provided in the cofferdam to discharge the internal gas of the cofferdam to the outside of the cofferdam; And

   Floating offshore structure comprising a valve provided in the supply pipe and the discharge pipe.
6. The method according to claim 4,

   The gas is a floating offshore structure including dry air (inert gas) or N2 gas.
7. The method according to claim 1,

   Further provided in the cofferdam heating unit for heating the cofferdam,

   The cofferdam is controlled to a sub-zero temperature to reduce the BOR (Boil-off Rate) generated by heat transfer from the cofferdam to the interior of the plurality of LNG storage tanks, but the sub-zero temperature is the heating portion of the heating image Floating offshore structures, characterized in that the temperature is changed to a specific temperature, including temperature.
8. The method according to claim 7,

   When the bulkhead of the cofferdam is made of a material that can withstand up to -30 ~ 0 ℃, the cofferdam is a floating offshore structure, characterized in that the temperature range in the range of -30 ~ 70 ℃.
9. The method according to claim 7,

   When the bulkhead of the cofferdam is made of low-temperature steel that can withstand up to -55 ℃, the cofferdam is a floating offshore structure, characterized in that the temperature range in the range of -55 ~ 70 ℃.
10. The method according to claim 7,

    When the fuel consumption of the floating offshore structure is large, the temperature of the cofferdam is increased to increase the generation of BOG (Boil-off Gas) and use it as fuel.

    Floating offshore structure, characterized in that to reduce the occurrence of the BOG by lowering the temperature of the cofferdam when the fuel consumption of the offshore structure is small.
11. The method according to claim 7,

    When the internal pressure of the LNG storage tank is greater than the set pressure of the LNG storage tank, the set temperature of the cofferdam is lowered, and when the internal pressure of the LNG storage tank is less than the set pressure of the LNG storage tank, the set temperature of the cofferdam Floating offshore structure, characterized in that to increase.
12. The method according to claim 7,

    The heating unit heats at least one of a trunk deck space controlled to a sub-zero temperature and a side passage way in contact with the trunk deck to heat the trunk deck space and the side passages of the image. Floating offshore structures, characterized in that by varying the temperature to a specific temperature.
13. The method according to claim 1,

    Floating offshore structure, characterized in that it further comprises a heat insulating material provided in the cofferdam.
14. The method according to claim 13,

    The cofferdam includes a plurality of lateral cofferdam for dividing the plurality of LNG storage tank in the lateral direction,

    The insulation is provided in the foremost front bulkhead of the transverse cofferdam disposed at the foremost of the plurality of transverse cofferdams and at the rearmost bulkhead of the stern rearward of the transverse cofferdam arranged at the rear of the stern. Floating offshore structures.
15. The method according to claim 1,

    Floating offshore structure further comprises a gas supply for supplying gas to the cofferdam.
16. The method according to claim 15,

    The gas supply unit,

    A gas supply pipe provided in the cofferdam to supply gas supplied through a gas supply line into the cofferdam;

    A gas discharge pipe provided in the cofferdam to discharge the internal gas of the cofferdam to the outside of the cofferdam; And

    Floating offshore structure comprising an on-off valve provided in the gas supply pipe and the gas discharge pipe.
17. The method according to claim 15,

    The gas supplied into the cofferdam has a dew point temperature of -45 ~ -35 ℃, the pair of bulk heads is controlled 1 ~ 10 ℃ higher than the dew point temperature of the gas floating offshore structure .
18. The method according to claim 15,

    Floating offshore structure, characterized in that while maintaining the temperature of the cofferdam in the image while continuously injecting and venting (venting) the gas inside the cofferdam.
19. The method according to claim 15,

    Floating offshore structure, characterized in that to provide an environment that the operator can enter the interior of the cofferdam by raising the temperature of the cofferdam by continuously injecting and discharging the gas into the cofferdam.
20. The method according to claim 2,

    The bulk head does not extend to the outer hull and is connected only to the inner hull,

    The strength member connecting the outer hull and the inner hull is not contiguous with the bulk head to reduce the BOR (Boil-off Rate) generated by heat transfer between the bulk head and the LNG stored in the plurality of LNG storage tanks. Floating offshore feature.
21. The method of claim 20,

    The bulk head is controlled at a temperature of -163 ~ -50 ℃, aluminum or stainless steel

    Floating offshore structure, characterized in that made of cryogenic material including steel.
22. The method of claim 20,

    Further provided in the plurality of LNG storage tank further comprises a sealing and heat insulating unit for sealing and insulating the LNG,

    The sealing and heat insulating unit is a floating offshore structure, characterized in that not provided in the bulk head of the area where the plurality of LNG storage tank and the bulk head contact.
23. The method according to claim 22,

    Between the bulkhead and the inner hull placed at the forefront and at the rear of the fore

    The floating portion is provided, the space portion is provided with a heat insulating material.
24. Controlling the cofferdam to a certain sub-zero temperature to reduce BOR;

    Controlling the cofferdam to a specific temperature, including the temperature of the image, such that an operator enters the cofferdam controlled to a sub-zero temperature; And

    And controlling the cofferdam back to a certain sub-zero temperature when an operator exits the cofferdam.
25. The method of claim 24,

    The cofferdam is a temperature control method of the floating offshore structure, characterized in that the controlled in the temperature range of -55 ~ 70 ℃.

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