CN115258037A

CN115258037A - Roll-on/roll-off vessel comprising a tank for storing liquefied gas

Info

Publication number: CN115258037A
Application number: CN202210470231.3A
Authority: CN
Inventors: 钦·利姆; 让-纪尧姆·梅泽奥
Original assignee: Gaztransport et Technigaz SA
Current assignee: Gaztransport et Technigaz SA
Priority date: 2021-04-30
Filing date: 2022-04-28
Publication date: 2022-11-01
Also published as: JP2022171598A; FR3122401B1; FR3122401A1; KR20220149456A

Abstract

The invention relates to a roll-on/roll-off vessel (1) comprising: -a hull (3) comprising a bottom (4) with a double wall; -a plurality of intermediate decks including a main loading/unloading deck (8); -at least one loading/unloading ramp; -a load bearing column (11) extending in a height direction (H); -a machine room; -a sealed and thermally insulated tank (2) for storage of liquefied gas, wherein the tank (2) is located below the main loading/unloading deck (8) and against the inner wall (5) of the bottom (4); -cofferdam walls (22) comprising an inner skin (23) and an outer skin (24), wherein each longitudinal tank wall is fixed to the inner skin (23) of one of the longitudinal cofferdam walls (22), and wherein at least one column of the first row or at least one column of the second row is located in one of the longitudinal cofferdam walls.

Description

Roll-on/roll-off vessel comprising a tank for storing liquefied gas

Technical Field

The present invention relates to the field of roll-on/roll-off (RO/RO) vessels for transporting self-propelled or towed wheeled cargo, such as vehicles, using one or more entry ramps to board the vessel. More specifically, the invention relates to the field of roll-on/roll-off vessels comprising sealed and thermally insulated membrane tanks for storage of liquefied natural gas at low temperatures. The tank is designed to receive liquefied gas as fuel for propelling the ro/ro-ro vessel.

In one embodiment, the liquefied gas is LNG, a mixture with high methane content stored at atmospheric pressure at a temperature of about-162 ℃. Other liquefied natural gases, such as ethane, propane, butane, liquefied Petroleum Gas (LPG) or ethylene are also contemplated.

Background

Rolling/roll-off vessels for transporting self-propelled or towed wheeled cargo are known in the prior art.

These vessels have: a hull including a base and an outer deck, the outer deck being spaced apart from the base in a height direction; a plurality of intermediate decks positioned between the bottom of the hull and the outer decks, in particular a main loading/unloading deck and one or more storage decks; a loading/unloading ramp connected to the main loading/unloading deck; and a load supporting column extending in height direction such that a first end is fixed to the bottom and a second end is fixed to e.g. an outer deck. The load bearing columns are usually arranged in rows of columns in the longitudinal direction of the vessel. The main loading/unloading deck thus corresponds to the fixed deck, onto which the cargo is brought via one or more loading/unloading ramps, for loading or unloading the cargo.

These load support columns play a crucial role in the stiffness of the hull of the vessel, since, unlike conventional vessels, roll-on/roll-off vessels do not have bulkheads which separate the interior of the hull and at the same time ensure the stiffness of the hull. This lack of bulkheads is necessary to allow self-propelled or towed wheeled cargo to move around on the intermediate deck.

The fuels mainly used by this type of ships comprise petroleum products, such as Heavy Fuel Oil (HFO), which has a boiling point much higher than ambient temperature, for example a boiling point between 120 and 600 ℃. The prior art vessels carry one or more tanks in their hull for storing such fuel. These tanks do not require any special equipment, since their contents can be stored in liquid form at ambient temperature. Such tanks do not therefore pose any problem in the location where they are placed in the ship, and are for example placed in free areas of the ship, such as the side edges.

However, due to the increasingly strict regulations regarding greenhouse gas emissions, in particular for marine transport, these rolling/rolling ships need to change their propulsion technology.

Compared to conventional heavy fuel oil, combustion of LNG can result in 100% reduction in sulfur oxides and particulates, 80% reduction in nitrogen oxides, and 20% reduction in carbon dioxide. Currently, LNG is the most efficient carbon fuel from a technical, operational and environmental perspective.

Disclosure of Invention

The idea forming the basis of the present invention is to position and size tanks for storing liquefied fuel gas in a roll-on/roll-off ship.

According to one embodiment, the invention provides a roll-on/roll-off vessel comprising:

-a hull comprising a double-walled bottom and an outer deck, the outer deck being spaced apart from the bottom in height direction, the double-walled bottom comprising an inner wall and an outer wall,

-a plurality of intermediate decks positioned between the bottom of the hull and the outer decks, the plurality of intermediate decks including a main loading/unloading deck and one or more storage decks,

-load bearing columns, each having a lower end fixed to the hull bottom and each extending in height direction through and supporting the intermediate deck, the load bearing columns being arranged in at least a first row of columns and a second row of columns, the load bearing columns of the same row being spaced apart from each other in the longitudinal direction of the vessel,

-a machine room located in the hull and comprising a propulsion system,

a sealed and thermally insulated tank for storing liquefied fuel gas for supplying the propulsion system with fuel gas, the tank comprising two longitudinal walls spaced apart from each other in a transverse direction, the transverse direction being perpendicular with respect to the longitudinal direction and the height direction of the vessel,

-cofferdam (cofferdam) walls comprising two longitudinal cofferdam walls, each cofferdam wall comprising an inner skin and an outer skin spaced apart from the inner skin,

wherein each longitudinal tank wall is fixed to the inner skin of one of the longitudinal cofferdam walls,

and wherein at least one load supporting column of the first row of columns or at least one load supporting column of the second row of columns is located in one of the longitudinal cofferdam walls.

By means of these features, the position and size of the tanks can be adapted to the specific structure of the roll-on/roll-off vessel without major structural changes involving a large number of structural recalculations. In particular, the position of the tank between the columns makes it possible to maintain the same load bearing column arrangement. Furthermore, by positioning at least one of the columns adjacent to the tank in the longitudinal cofferdam wall, the transverse dimension of the tank can be increased or even maximized without changing the arrangement of the columns in the hull of the vessel.

According to some embodiments, such a vessel may comprise one or more of the following features.

According to one embodiment at least one load supporting column of the first row of columns is located in one of the longitudinal cofferdam walls and at least one load supporting column of the second row of columns is located in the other of the longitudinal cofferdam walls.

According to one embodiment the roll-on/roll-off vessel comprises at least one loading/unloading ramp connected to the main loading/unloading deck.

According to one embodiment, the sealed and thermally insulated tank is a membrane tank, preferably a tank configured for storage of LNG.

According to one embodiment the tank has a longitudinal dimension extending in the longitudinal direction, the longitudinal dimension of the tank being adjustable between the machine room and the front part of the vessel according to the maximum volume of liquefied gas required.

According to one embodiment, the main loading/unloading deck is fixed and the at least one storage deck is movable in height direction, thereby changing the distance between two adjacent intermediate decks for placing large cargo.

According to one embodiment the storage deck located above or below the main loading/unloading deck is movable in height direction.

According to one embodiment, at least one load bearing column, a plurality of load bearing columns or each load bearing column extends in height direction through and supports all intermediate decks.

According to one embodiment, the or each load support column has an upper end fixed to the outer deck.

According to one embodiment, one or more cofferdam walls are made of metal, such as steel.

According to one embodiment, the inner skin and/or the outer skin are formed by sheet metal layers, for example steel layers.

According to one embodiment, the load bearing column is made of metal, such as steel.

According to one embodiment said at least one load supporting column located in one of the longitudinal cofferdam walls is made of a higher steel grade than the steel grade of the other load supporting columns.

The temperature in the cofferdam walls adjacent to the tanks may thus be lower than in other parts of the vessel, since these cofferdam walls are close to the tanks for storage of liquefied gas. The higher steel grade used for the column makes it possible to counteract this temperature difference, thus maintaining sufficient mechanical strength.

The steel grade in this case is the steel grade comprising the designation symbol-based steel under the generic term non-alloyed steel in the EN-10027-1-2 standard. In the name of this steel, the first letter designates the use of the steel, followed by a number indicating the yield strength in mpa. For example, S235 represents a non-alloy structural steel having a yield strength of 235 MPa. The term "higher steel grade" thus means in this case a steel grade with a higher yield strength for the same use. In addition, IGF regulations (international safety regulations for ships using gas or other low flash point fuels) also use symbolic-based steel names to classify different steel grades. In particular, in this rule, the symbol for steel grade is a letter or a pair of letters, the higher steel grade being represented by the higher first letter of the alphabet, e.g., steel grade B is higher than steel grade a.

In another embodiment, the at least one load support column located in the cofferdam wall may be made of the same steel grade as the steel grade of the other load support columns.

According to one embodiment said at least one load supporting column located in the longitudinal cofferdam wall is made of steel with a yield strength greater or equal compared to the steel of the other load supporting columns.

According to one embodiment said at least one load bearing column in the first row of columns is formed against the inner or outer skin of the longitudinal cofferdam wall.

By positioning the load bearing columns against the inner skin, the transverse dimensions of the tank can be optimized to the maximum extent without affecting the position of the load bearing columns, which in this case are subjected to thermal and mechanical stresses to be taken into account due to their proximity to the structure of the tank. In particular, in this case, the gain in the transverse dimension is equal to the spacing between the inner and outer skins. On the other hand, if the load bearing columns are positioned against the outer skin, they are less subjected to thermal and mechanical stresses from the tank, but the gain in the transverse dimension is correspondingly reduced.

According to one embodiment said at least one load bearing column in the second row of columns is formed against the inner or outer skin of the longitudinal cofferdam wall.

According to one embodiment, the inner and outer skins of the longitudinal cofferdam wall comprise reinforcing members protruding in the transverse direction to rigidify the inner and outer skins.

The load-bearing columns positioned against the inner or outer skin of the longitudinal cofferdam wall also contribute to the rigidity of this skin, and more preferably they make it possible to dispense with some of these reinforcements.

According to one embodiment the load bearing columns have a dimension in the transverse direction of between 100mm and 400mm, for example 400mm, the inner and outer skins of the longitudinal cofferdam walls being spaced from each other in the transverse direction preferably by a distance of at least 900mm, more preferably by a distance of between 900mm and 1200 mm.

According to one embodiment, the tank has a parallelepiped shape.

According to one embodiment, the tank comprises: a rear tank wall separated from the machine room by a rear cofferdam wall; a front tank wall spaced apart from the rear tank wall in the longitudinal direction of the vessel; a bottom tank wall, preferably positioned against an interior wall of the bottom of the hull; a top tank wall spaced apart in height from the bottom tank wall; and two longitudinal tank walls.

According to one embodiment, the can has the shape of a polyhedron comprising eight or ten faces.

According to one embodiment the tank is located elevationally below the main loading/unloading deck and against the inner wall of the bottom of the hull.

The entire tank is thus located between the double-walled bottom and the main loading/unloading deck, so that the tank does not obstruct loading and unloading and therefore does not require any changes to the movement of the cargo.

According to one embodiment the vessel comprises a tank connection space, a tank valve and at least one dome located in the tank connection space, the tank connection space being located on the top wall of the tank and below the main loading/unloading deck in height direction.

Thus, the tank connection space is also located between the double-walled bottom and the main loading/unloading deck, so that the tank connection space does not hinder loading and unloading and therefore does not require any changes to the movement of the cargo.

According to one embodiment, each tank comprises a multilayer structure comprising, from the outside to the inside of the tank: a secondary thermal insulation barrier; a secondary sealing film positioned against the secondary thermal insulation barrier; a primary thermal insulation barrier positioned against the secondary sealing film; and a primary sealing membrane positioned against the primary thermal insulation barrier and intended to be in contact with the liquefied gas.

According to one embodiment, the present invention also provides a transfer system for transferring liquefied gas, the system comprising: a roll-on/roll-off vessel as described above; an insulated pipeline arranged to connect a tank installed in the hull of a ro/ro-ro vessel to a floating or onshore storage facility; and a pump for pumping the cold liquid product stream from the floating or onshore storage facility to the tanks of the ro/ro-ro vessel via insulated pipelines.

According to one embodiment, the invention also provides a method for loading a roll-on/roll-off vessel as described above, in which method liquefied gas is transferred from a floating or onshore storage facility to the tanks of the roll-on/roll-off vessel via insulated pipelines.

Drawings

The invention will be better understood and other objects, details, characteristics and advantages thereof will appear more clearly in the following description of a number of particular embodiments of the invention, given purely by way of non-limiting example, with reference to the accompanying drawings.

Fig. 1 shows a side view of the interior of a roll-on/roll-off vessel according to one embodiment.

Fig. 2 is a view of detail II of fig. 1, particularly showing the storage tanks in the hull of the ship.

Fig. 3 is a partial section of fig. 1 taken along the plane III-III, showing the arrangement of the load support column in the transverse direction with respect to the storage tank according to the first embodiment.

Fig. 4 is a cross-sectional view of fig. 1 taken along the plane IV-IV, showing the arrangement of the load support columns in the longitudinal direction with respect to the storage tank according to the first embodiment.

Fig. 5 is a view of detail V of fig. 4, particularly showing a portion of the storage tank and the load support column.

Fig. 6 schematically shows a roll-on/roll-off ship comprising a tank for storage of liquefied fuel gas and a quay for loading the tank.

Detailed Description

A roll-on/roll-off vessel 1 according to various embodiments is described below with reference to fig. 1 to 6.

As mentioned above, the roll-on/roll-off vessel 1 has a specific structure that allows self-propelled or towed wheeled cargo to move freely between the various decks, the vessel 1 allowing cargo to enter the vessel 1 in its own manner and to leave the vessel 1 in the same manner. Such cargo may for example comprise automobiles, road transport vehicles and their cargo (tractor trailers, articulated lorries), heavy construction machinery, agricultural equipment such as tractors, or accommodations mounted on loading/unloading vehicles such as forklifts or trailers.

Thus, unlike a conventional cargo ship, where cargo is loaded vertically by means of a lifting device such as a crane, in this case the cargo is loaded and unloaded by driving the cargo onto and off the ship using a movable loading/unloading ramp 10, which movable loading/unloading ramp 10 is connected to a ramp mounted on a quay at a port or directly on the quay.

To this end, the roll-on/roll-off vessel 1 comprises:

a hull 3, which hull 3 comprises a double-walled bottom 4 and an outer deck 7, which outer deck 7 is spaced apart from the bottom 4 in height direction H,

a plurality of

intermediate decks

8, 9, said plurality of

intermediate decks

8, 9 being positioned between the bottom 4 of the hull 3 and the outer decks 7, said plurality of intermediate decks comprising a main loading/unloading deck 8 and one or more storage decks 9,

at least one loading/unloading ramp 10 connected to the main loading/unloading deck 8,

a load bearing column 11, which load bearing column 11 extends in height direction through the

intermediate decks

8, 9 and supports the

intermediate decks

8, 9,

a machine room 14, which machine room 14 is located in the hull 3 and comprises a propulsion system 15,

a sealed and thermally insulated membrane tank 2, the membrane tank 2 being used for storing liquefied fuel gas for supplying the fuel gas to the propulsion system 15.

The double-walled bottom 4 consists of an inner wall 5 and an outer wall 6. The load bearing column 11 thus has a lower end fixed to the inner wall 5 of the bottom 4 and an upper end that can be fixed to the outer deck 7.

In the example shown in fig. 5 and 6, the load bearing columns 11 are arranged in a first row of columns 12 and a second row of columns 13. The load bearing columns 11 of the

same row

12, 13 are spaced apart from each other in the longitudinal direction L of the vessel 1. Furthermore, the two

rows

12, 13 are positioned symmetrically in the transverse direction T, so as to stiffen the hull 3 in a balanced manner over the entire length of the vessel 1. In other embodiments not shown, the load bearing columns 11 may be arranged in more than two rows, for example four rows, and preferably in even number rows.

Fig. 1 shows a roll-on/roll-off vessel 1 according to one design example. In particular, in this example, the roll-on/roll-off vessel 1 comprises twelve intermediate decks, so the roll-on/roll-off vessel 1 comprises eleven storage decks 9 and one main loading/unloading deck 8. The inner wall 5 of the bottom 4 also serves as a storage deck 9 and is generally considered as a first deck, each deck being designated by its number, from the lowest deck to the highest deck in the height direction H of the vessel 1. For this design the main loading/unloading deck 8 is thus the fifth deck. The

intermediate decks

8, 9 and the inner wall 5 are connected to each other by means of an entrance ramp 16 or a vertical lift system.

The structure of the tank 2 and the position and dimensions of the tank 2 in the hull 3 of the vessel 1 will now be described in more detail below.

As can be seen in fig. 2, in this case the tank 2 has a parallelepiped shape and the tank 2 has a plurality of tank walls, namely: a rear tank wall 17; a front tank wall 18 opposite the rear tank wall 17; a bottom wall 19; a top wall 20 opposite the bottom wall 19; and two longitudinal walls 21. The bottom wall 19 is positioned against the inner wall 5 of the bottom 4.

In addition to the bottom wall 19, the

other tank walls

17, 18, 20, 21 are fixed to a cofferdam wall 22, said cofferdam wall 22 forming, together with the inner wall 5 of the hull 4, a load bearing structure of the tank 2, as can be seen in fig. 2-4. The cofferdam wall 22 consists of an inner skin 23 and an outer skin 24, the

tank walls

17, 18, 20, 21 being fixed to this inner skin 23, this outer skin 24 being spaced apart from the inner skin 23. The reinforcement 25 is placed inside the cofferdam wall 22 and on the inner skin 23 and the outer skin 24, thus rigidizing each of the

skins

23, 24.

The tank 2 is placed in the hull 3 so that one of the cofferdam walls 22 separates the machine room 14 and the rear tank wall 17, as shown in fig. 2. In this case the machine room 14 is positioned against the inner wall 5 of the bottom 4 at the rear of the vessel 1 with respect to the longitudinal direction L of the vessel 1.

Each tank wall 17 to 21 comprises a multilayer structure comprising, from the outside to the inside of the tank: a secondary thermal insulation barrier; a secondary sealing film positioned against the secondary thermal insulation barrier; a primary thermal insulation barrier positioned against the secondary sealing membrane; and a primary sealing membrane positioned against the primary thermal insulation barrier and intended to be in contact with the liquefied fuel gas. Examples of such membrane tanks are described in particular in patent applications WO2019239048, WO14057221, FR2691520 and FR 2877638. In particular, the membrane tank may use GTT technology developed by the applicant

Mark

Mark

And

to perform the construction.

As can be seen in fig. 2, above the top wall 20 there is a tank connection space 26, which tank connection space 26 is surrounded by a cofferdam wall 22. The tank connection space 26 comprises in particular a dome 27, through which dome 27 in particular a loading pipe 28 passes through the top wall 20 for filling the tank 2 with liquefied fuel gas. The tank connection space 26 is a safe space in which the pipes through the top wall 20 are connected to other equipment of the vessel, such as tank valves.

The vessel 1 also has a fuel preparation room 29, which fuel preparation room 29 is positioned adjacent to one of the longitudinal walls 21 of the tank 2 and the machine room 14, as can be seen in fig. 5 and 6. The fuel preparation chamber 29 is equipped in particular with means for conditioning the fuel gas so as to adjust the pressure and temperature of the fuel gas to values suitable for the propulsion system 15.

Thus, the tanks 2, cofferdam walls 22 and tank connection spaces 26 are dimensioned to be positioned below the main loading/unloading deck 8, as shown in fig. 2. In particular, in the design example of fig. 2, the highest of the cofferdam walls 22, i.e. the cofferdam wall located above the tank connection space 26, is located on the fourth deck, i.e. one of the storage decks 9. Thus the structure of tank 2 and the equipment of the tank and tank connection space 26 do not affect the design of main loading/unloading deck 8.

Fig. 3 shows one embodiment as to the position and size of the tank 2 relative to the load support column 11.

In the figure, a distinction can be made between a deck from the first to the fifth deck, the tank 2 and one of the load support columns 11 of the first row of columns. Since the design is symmetrical in the transverse direction T, only half of the cross section of the vessel 1 is shown. Thus, in the design example shown in fig. 3 and 4, the second deck and the fourth deck as storage deck 9 are decks which are movable in height direction H, while the third deck as storage deck 9 and the fifth deck as main loading/unloading deck 8 are decks which are fixed in height direction H. The fixed deck is designed so that it can support heavier loads than the movable deck.

In the embodiment of fig. 3, one of the load supporting columns 11 of the first row of columns 12 is located in one of the longitudinal cofferdam walls 22, i.e. against the inner skin 23. Thus, the configuration of the tank 2 and cofferdam wall 22 does not affect the design and location of the load support columns 11. Furthermore, in this case it is possible to obtain a tank with an increased transverse dimension to the maximum extent without affecting the position of the load-bearing column 11. The gain in width of the tank 2 is substantially equal to the transverse dimension of the longitudinal cofferdam wall 22.

In another embodiment, not shown, one of the load-bearing columns 11 of the first row of columns 12 may be located in one of the longitudinal cofferdam walls 22, but this time against the outer skin 24. Thus, the configuration of the tank 2 and cofferdam wall 22, as above, does not affect the design and location of the load support columns 11.

Thus, it can be seen that the load bearing columns of each row of

columns

12, 13 are substantially aligned in the longitudinal direction L.

Fig. 4 and 5 show a section of the vessel 1, wherein the arrangement of all load support columns 11 of each row of

columns

12, 13 and tanks 2 and cofferdam walls 22 relative to these load support columns 11 can be seen.

In particular, as can be seen in the detailed view of fig. 5, in this embodiment, three load bearing columns 11 of each row of

columns

12, 13 are arranged in the longitudinal cofferdam wall 22. The number of load bearing columns located in the cofferdam wall 22 depends on the length of the vessel 1, the total number of columns and the length of the tank 1 in the longitudinal direction.

Referring to fig. 6, a view of a partially cut-away roll-on/roll-off vessel 1 shows a substantially parallelepiped shaped sealed and thermally insulated tank 2 fitted in the hull 3 of the vessel 1. As is known, the loading line 73 for filling the ship may be connected to a marine or harbour terminal by means of suitable connections for transferring LNG cargo to the tanks 2.

Figure 6 shows an example of a marine terminal comprising a loading and unloading station 75, a subsea pipeline 76 and an onshore facility 77. The loading station 75 is a fixed offshore installation, the loading station 75 comprising a movable arm 74 and a tower 78, the tower 78 supporting the movable arm 74. The movable arm 74 carries a bundle of insulated flexible tubing 79 which can be connected to the loading line 73. The orientable moveable arm 74 can be adjusted to suit all sizes of boat. A connecting conduit (not shown) extends inside the tower 78. The loading station 75 allows loading of the ro/ro-ro vessel 1 with LNG fuel from an onshore facility 77. The installation comprises a tank 80 for storing liquefied gas and a connecting pipeline 81, the connecting pipeline 81 being connected to the loading station 75 by means of the underwater pipeline 76. The underwater pipeline 76 allows the transfer of liquefied gas over a long distance, e.g. 5km, between the loading station 75 and the onshore facility 77, which makes it possible to keep the roll-on/roll-off vessel 1 at a great distance from shore during the loading operation.

To generate the pressure necessary for the transfer of the liquefied gas, pumps on board the vessel 1 and/or pumps fitted to onshore facilities 77 and/or pumps fitted to the loading station 75 can be used.

Although the invention has been described with reference to a number of specific embodiments, it is clear that the invention is in no way limited thereto and that the invention comprises all technical equivalents of the measures described as well as combinations of these technical equivalents if they fall within the scope of the invention.

Use of the verb "comprise" or "comprise" and its conjugations does not exclude the presence of elements or other stages other than those stated in a claim.

In the claims, any reference signs placed between parentheses shall not be construed as limiting the claim.

Claims

1. A roll-on/roll-off vessel (1) comprising:

-a hull (3), said hull (3) comprising a double-walled bottom (4) and an outer deck (7), said outer deck (7) being spaced apart from said bottom (4) in the height direction (H), said bottom (4) with double walls comprising an inner wall (5) and an outer wall (6),

-a plurality of intermediate decks positioned between the bottom (4) of the hull (3) and the outer decks (7), including a main loading/unloading deck (8) and one or more storage decks (9),

-load bearing columns (11), each load bearing column (11) having a lower end fixed to the bottom (4) of the hull (3) and each load bearing column (11) extending in the height direction (H) through and supporting the intermediate deck, the load bearing columns (11) being arranged in at least a first row of columns (12) and a second row of columns (13), the load bearing columns (11) of the same row being spaced apart from each other in the longitudinal direction (L) of the vessel,

-a machine room (14), the machine room (14) being located in the hull (3) and comprising a propulsion system (15),

-a sealed and thermally insulated tank (2), the tank (2) being for storing liquefied fuel gas for supplying the fuel gas to the propulsion system (15), the tank (2) comprising two longitudinal walls (21) spaced from each other in a transverse direction (T), the transverse direction (T) being perpendicular with respect to the longitudinal direction (L) and the height direction (H) of the vessel,

-a cofferdam wall (22), said cofferdam wall (22) comprising two longitudinal cofferdam walls (22), each longitudinal cofferdam wall (22) comprising an inner skin (23) and an outer skin (24) spaced apart from said inner skin (23),

wherein each longitudinal tank wall (21) is fixed to the inner skin (23) of one of the longitudinal cofferdam walls (22),

and wherein at least one load supporting column (11) of the first row of columns (12) or at least one load supporting column (11) of the second row of columns (13) is located in one of the longitudinal cofferdam walls (22).

2. Roll-on/roll-off vessel (1) according to claim 1, wherein at least one load supporting column (11) of the first row of columns (12) is located in one of the longitudinal cofferdam walls (22) and at least one load supporting column (11) of the second row of columns (13) is located in the other one of the longitudinal cofferdam walls (22).

3. Roll-on/roll-off vessel (1) according to claim 1 or 2, wherein at least one of the load bearing columns (11) in the first row of columns (12) or at least one of the load bearing columns (11) in the second row of columns (13) is formed against the inner skin (23) or the outer skin (24) of the longitudinal cofferdam wall (22).

4. Roll-on/roll-off vessel (1) according to one of claims 1 to 3, wherein the load bearing columns (11) have a dimension in the transverse direction (T) of between 100mm and 400mm, the inner skin (23) and the outer skin (24) of the longitudinal cofferdam wall (22) being spaced from each other in the transverse direction (T), preferably by a distance of at least 900 mm.

5. The roll-on/roll-off vessel (1) according to one of claims 1 to 4, wherein the tank (2) has a parallelepiped shape and the tank (2) comprises:

a rear tank wall (17), said rear tank wall (17) being separated from said machine room (14) by a rear cofferdam wall (22);

a front tank wall (18), the front tank wall (18) being spaced apart from the rear tank wall (17) in the longitudinal direction (L) of the roll-on/roll-off vessel;

a bottom tank wall (19), said bottom tank wall (19) preferably being positioned against said inner wall (5) of said bottom (4) of said hull (3);

a top tank wall (20), the top tank wall (20) being spaced apart from the bottom tank wall (19) in the height direction (H); and

two of said longitudinal tank walls.

6. Roll-on/roll-off vessel (1) according to one of the claims 1 to 5, wherein the load bearing columns are made of metal.

7. Roll-on/roll-off vessel (1) according to claim 6, wherein the at least one load supporting column in one of the longitudinal cofferdam walls is made of the following steel grades: the steel grade is equal to or higher than the steel grade of other load supporting columns.

8. Roll-on/roll-off vessel (1) according to one of claims 1-7, wherein each load bearing column extends in the elevation direction through and supports all the intermediate decks.

9. Roll-on/roll-off vessel (1) according to claim 8, wherein each load bearing column has an upper end fixed to the outer deck.

10. Roll-on/roll-off vessel (1) according to one of claims 1 to 9, wherein each tank wall (17, 18, 19, 20, 21) comprises a multilayer structure comprising from the outside to the inside of the tank (2):

a secondary thermal insulation barrier;

a secondary sealing film positioned against the secondary thermal insulation barrier;

a primary thermal insulation barrier positioned against the secondary sealing film; and

a primary sealing membrane positioned against the primary thermal insulation barrier and intended to be in contact with the liquefied gas.

11. A delivery system for delivering liquefied fuel gas, the system comprising:

roll-on/roll-off vessel (1) according to one of claims 1 to 10;

an insulated pipeline (73, 79, 76, 81), the insulated pipeline (73, 79, 76, 81) being arranged to connect the tanks (2) installed in the hull (3) of the roll-on/roll-off vessel (1) to a floating or onshore storage facility (77); and

a pump for pumping a cold liquid product stream from the floating or onshore storage facility to the tanks (2) of the ro/ro-landing vessel (1) through the insulated pipeline.

12. Method for loading a roll-off/roll-off vessel (1) according to one of claims 1 to 10, wherein liquefied fuel gas is transferred from a floating or onshore storage facility (77) to the tanks (2) of the roll-off/roll-off vessel (1) through the insulated pipelines (73, 79, 76, 81).