WO2018065658A1

WO2018065658A1 - A fuel tank unit

Info

Publication number: WO2018065658A1
Application number: PCT/FI2016/050693
Authority: WO
Inventors: Luca BOARO; Andrea Zotti
Original assignee: Wärtsilä Finland Oy
Priority date: 2016-10-05
Filing date: 2016-10-05
Publication date: 2018-04-12
Also published as: KR102028871B1; EP3523567A1; CN109790956B; CA3036925C; EP3523567B1; CN109790956A; CA3036925A1; KR20190055126A

Abstract

Invention relates to a fuel tank unit (10) for storing liquefied gas fuel and another liquid in a common unit, the unit comprising a first fuel tank (14) for liquefied gas fuel and a second tank (16) for a second liquid. The first fuel tank (14) is enclosed by a first shell (18) and the first shell (18) is enclosed by a second shell (20) wherein the heat insulation (24) is arranged between the first shell (18) and the second shell (20), and the second shell (20) is at least partially enclosed by a third shell (22) wherein the second tank (16) is arranged between the second shell (20) and the third shell (22).

Description

A fuel tank unit

Technical field

[001 ] The present invention relates to a fuel tank unit for storing liquefied gas fuel and liquid fuel comprising a first fuel tank for liquefied gas fuel and a second fuel tank for liquid fuel according to the preamble of claim 1 .

Background art

[002] Internal combustion piston engines which are configured to operate using more than one fuel in the combustion need several fuel systems respectively. This means also that separate fuel tanks are needed for each one of the fuels. As an example such engine is an engine using a first fuel as a main fuel and a second fuel as a pilot fuel for igniting the first fuel. Particularly in marine vessels and land based power plant a large gas engine may be used where the main fuel is gaseous fuel which is stored as liquefied gas and the pilot fuel is liquid fuel such as light fuel oil or marine diesel oil.

[003] For example natural gas is in gaseous form in room temperature. In marine vessels that use natural gas as fuel in its power plant, the natural gas is typically stored onboard in liquid form as liquefied natural gas. Natural gas can be kept in liquid form by maintaining its temperature below its boiling point, which is approximately - 163 °C. Typically LNG tank is a cylindrical, double-walled or single- walled, insulated tank.

[004] WO2016097461 A1 discloses an LNG tank located in a tank hold space of a marine vessel comprising an inner metal shell, an outer metal shell and an isolation space between the shells advantageously containing vacuum. The document also shows schematically the architecture of a known fuel system onboard an LNG-fuelled ship.

[005] WO 2016087705 A1 discloses a sea-going vessel which comprises one or more engines, of which at least one is operable using a first fuel and at least one using a second fuel, the engine(s) being configured to receive the first fuel in liquid state and the second fuel in gaseous state or as a supercritical fluid. A first fuel tank for the first fuel is arranged on a first side of the vessel, a second fuel tank for the first fuel is are ranged on a second side of the vessel, and a third fuel tank for the second fuel is arranged between the first fuel tank and the second fuel tank. The fuel tanks are separated by a transverse bulkhead from an engine room of the vessel. As can be observed from the document the positioning the fuel tanks into a marine vessel can be cumbersome and space consuming and the space in the vessel needs to be used as efficiently as possible [006] Document EP 3012509 A1 discloses a horizontal type cylindrical double-shell tank which includes an inner shell and an outer shell. The inner shell includes an inner shell main part storing a liquefied gas. The outer shell forms a vacuum space between the inner shell and the outer shell. The tank includes a tank cover covering the double-shell tank. A space between the double-shell tank and the tank cover may be filled with air. However, desirably, an inert gas is enclosed in the space. Examples of the inert gas include nitrogen and argon. By enclosing such an inert gas, in a case where the liquefied gas is, for example, ultracold liquefied hydrogen, liquefied oxygen can be prevented from being generated around tank-supporting units, which are greatly affected by heat from the inner shell. [007] An object of the invention is to provide a fuel tank in which storage efficiency is considerably improved compared to the prior art solutions.

Disclosure of the Invention

[008] The objects of the invention can be met substantially as is disclosed in the independent claim and in the other claims describing more details of different embodiments of the invention.

[009] A fuel tank unit according to an embodiment of the invention is configured to store a first liquid, which is liquefied gas fuel and a second liquid in the common fuel tank unit. Thus, the fuel tank unit comprises a first fuel tank for liquefied gas fuel and a second tank for the second liquid. The first fuel tank is enclosed by a first shell and the first shell is enclosed by a second shell wherein a vacuum heat insulation is arranged between the first shell and the second shell, and the second shell is at least partially enclosed by a third shell wherein the fuel tank is arranged between the second shell and the third shell. [0010] A fuel tank unit according to another embodiment of the invention is configured to store liquefied gas fuel and another liquid in the common fuel tank unit. Thus, the fuel tank unit comprises a first fuel tank for liquefied gas fuel and a second fuel tank for liquid fuel. The first fuel tank is enclosed by a first shell and the first shell is enclosed by a second shell wherein a vacuum heat insulation is arranged between the first shell and the second shell, and the second shell is at least partially enclosed by a third shell wherein the second fuel tank is arranged between the second shell and the third shell.

[001 1] Such a fuel tank is particularly advantageous in storing fuels for use in marine vessels and land based power plant provided with a large gas engine where the main fuel is gaseous fuel which is stored as liquefied gas and the pilot fuel is liquid fuel such as light fuel oil or marine diesel oil.

[0012] According to an embodiment of the invention the second shell is completely enclosed by the third shell where the volume of the second tank may be maximized while having both the main fuel and the pilot for a dual fuel engine stored using a footprint area of substantially one fuel tank only.

[0013] According to an embodiment of the invention the fuel tank unit is of elongated form having a length, width, height and longitudinal axis lengthwise the unit, and the second shell has, perpendicular to the longitudinal axis, a circular cross section.

[0014] According to an embodiment of the invention the third shell has, perpendicular to the longitudinal axis, a cross section which advantageously is arranged inside a rectangle the sidewalls of which are tangential to the second shell.

[0015] According to an embodiment of the invention the fuel tank unit is of elongated form having a length, width, height and longitudinal axis lengthwise the unit, and the second shell has, perpendicular to the longitudinal axis, a circular cross section and that the third shell has, perpendicular to the longitudinal axis, a rectangular cross sectional shape. [0016] According to an embodiment of the invention at least one wall of the third shell is against to the second shell.

[0017] According to an embodiment of the invention at least two walls of the third shell are against to the second shell. [0018] According to an embodiment of the invention the at least two walls of the third shell are in the vicinity of the second shell.

[0019] According to an embodiment of the invention the at least two walls of the third wall are tangential to the second shell.

[0020] According to an embodiment of the invention all of the walls of the third shell are tangential to the second shell.

[0021] According to an embodiment of the invention the first and the second shells have, perpendicular to the longitudinal axis, a circular cross section.

[0022] According to an embodiment of the invention the heat insulation between the first wall and the second wall is a vacuum insulation configured for insulation of cryo- genie liquefied gas.

[0023] According to an embodiment of the invention the unit comprises a fuel conduit extending through the second shell and the third shell and the vacuum insulation to the first tank and that the fuel conduit is enclosed with an insulation.

[0024] According to an embodiment of the invention the second tank comprises at least two separate compartments, wherein advantageously a first compartment of the second tank has a volume which is 1 - 5% of the volume of the first tank. The first compartment is configured to store necessary volume of pilot for to enable a gas mode operation of an internal combustion engine.

[0025] The invention provides considerable space savings when the both the main fuel and the pilot for a dual fuel engine can be stored using a footprint area of one fuel tank only.

[0026] According to an embodiment of the invention by configuring the second space suitably, it is possible to store for example fresh water and liquefied gas in the same fuel tank unit. This provides considerable space savings when the both the fuel and the second liquid, such as fresh water, can be stored using a footprint area of one fuel tank only.

[0027] The exemplary embodiments of the invention presented in this patent applica- tion are not to be interpreted to pose limitations to the applicability of the appended claims. The verb "to comprise" is used in this patent application as an open limitation that does not exclude the existence of also unrecited features. The features recited in depending claims are mutually freely combinable unless otherwise explicitly stated. The novel features which are considered as characteristic of the invention are set forth in particular in the appended claims.

Brief Description of Drawings

[0028] In the following, the invention will be described with reference to the accompanying exemplary, schematic drawings, in which Figure 1 illustrates a fuel tank unit according to an embodiment of the invention,

Figure 2 illustrates cross sectional view ll-ll of the figure 1 ,

Figures 3 - 8 illustrate cross sectional views ll-ll of the figure 1 according to different embodiments of the invention, and

Figure 9 illustrates a fuel tank unit according to another embodiment of the invention.

Detailed Description of Drawings

[0029] In the figures the principles of the invention is explained as an implementation where two different fuels are stored in the tank unit 10. Figure 1 illustrates, on a deck or a platform 12 of a marine vessel, a fuel tank unit 10 in accordance with a preferred embodiment of the present invention. Figure 2 illustrates the cross sectional view ll-ll of the figure 1. Now referring to the figures 1 and 2 the fuel tank unit 10 comprises a first fuel tank 14 for liquefied gas fuel enclosed by a first shell 18. The first fuel tank may be constructed as a pressure vessel depending on the actual application but it is at least arranged to withhold the cryogenic circumstances inside the first tank 14. The first shell 18 is enclosed also by a second shell 20 and there is a space between the first shell and the second shell 20 practically all over the first shell 18. The space is provided with heat insulation 24. The heat insulation 24 is advantageously a vacuum insulation. In the vacuum insulation the space between the first shell 18 and the second shell 20 is practically totally evacuated of air, creating a near-vacuum which significantly reduces heat transfer by conduction or convection through the space.

[0030] The fuel tank comprises further a second tank 16 for liquid fuel enclosed by a third shell 22. The third shell 22 encloses also the second shell 20. According to an embodiment of the invention the tank unit is configured to supply fuel to a so called dual fuel engine where the liquefied gas is used as the main fuel and the liquid fuel, such as a marine diesel oil or light fuel oil, is used as pilot fuel for igniting the main fuel in the engine. The first fuel tank 14 is enclosed by the second fuel tank 16. The second fuel tank 16 encloses also the heat insulation 24 arranged between the first and the second fuel tank.

[0031] The tank unit 10 is of elongated form having a length L, width W, height H and longitudinal axis A lengthwise the unit. As can be seen in the figure 2 the first shell 18 and the second shell 20 have a circular cross section perpendicular to the longitudinal axis A. Both the first and the second shell comprises a cylindrical part and dome-like end parts 18', 20' at the lengthwise ends of the cylindrical part. Respectively the third shell 22 I has, perpendicular to the longitudinal axis A, a rectangular cross sectional shape and end parts 22' at its ends.

[0032] As can be seen in the embodiment of figure 2 the width W of the tank unit corresponds substantially the width of the first fuel tank 14 and the height H of the tank unit 10 is only slightly higher than the height or the diameter of the first fuel tank 14. Here two of the walls of the third shell 22 are in contact with the second shell 20. The walls of the third wall are tangential to the second shell. This provides considerable space savings when the both the main fuel and the pilot for a dual fuel engine can be stored using a footprint area of one fuel tank only. In other words, when the cross section of the first fuel tank 14 is circular and the cross section of the second fuel tank 16 is rectangular or even square, the volume of the second tank 16 is mainly formed to the regions between the circular second shell 20 and the rectangular third shell 22. As mentioned earlier the space between the first shell 18 and the second shell 20 constitutes a heat insulation for the first fuel tank 14. In some applications it could be necessary to provide only one wall of the third shell 22 against to the second shell 20 but obtaining the benefit of the space savings to some extent. Also depending on the case at least two walls of the third shell are arranged only in the vicinity of the second shell i.e. there is a small gap arranged between the shells.

[0033] In the figure 3 there is shown an embodiment of the invention where all of the walls of the third shell are against and tangential to the second shell. This provides the most space-effective solution. Due to the shapes of the third 22 and the second 20 shells the different sections at the corners are in communication with each other at the ends of the tank unit 10.

[0034] In the figure 4 there is shown an embodiment of the invention where two of the walls of the third shell 22 are connected with each other by a rounded fillet complying with the rounded shape of the vessels deck structure 12 or a hull.

[0035] In the figure 5 there is shown an embodiment of the invention where the third shell 22 is integrated to the vessel's deck and/or hull structure. In other words, the vessel's deck and/or hull wall forms the third shell 22.

[0036] In the figure 6 there is shown an embodiment of the invention where the third shell 22 has, perpendicular to the longitudinal axis, a polygonal cross section. The polygonal third shell 22 is arranged inside an imaginary rectangle the sidewalls of which are tangential to the second shell 20.

[0037] In the figure 7 there is shown an embodiment of the invention where the third shell 22 encloses only partially the second shell 20. Here the second fuel tank 16 is arranged on top of the first fuel tank 14. The third shell comprises three side walls which are tangential to the second shell 20. Here the third shell 22 has one section the width of which is equal to the diameter of the second shell 20 and the other two sections having width which is equal to the radius of the second shell 20.

[0038] In the figure 8 there is shown another embodiment of the invention where the third shell 22 encloses only partially the second shell 20. Here the second fuel tank 16 is arranged to the end of the tank unit such that the third shell 22 covers substan- tially only the dome-like end part 20' of the second shell 20. Here the third shell 22 is circular having a diameter less than or equal to the diameter of the second shell 20. [0039] The heat insulation between the first wall and the second wall is a vacuum insulation configured for insulation of liquefied gas. The space may also be filled with expanded perlite particles. As an example, the heat conductivity of the heat insulation is below 0,0023— .

m K [0040] The fuel tank unit 10 is provided with a room or space 30 welded to, or by some other appropriate means arranged in connection with, the third shell 20 of the tank unit 10, the space 30 housing the piping, heaters, evaporators and other optional equipment, as well as instruments (now shown) needed when filling or emptying the fuel tank unit 10. The fuel tank unit 10 comprises at least two liquefied gas fuel con- duits 32 extending through the second shell 20 and the third shell 22 and the insulation to the first tank 14. The fuel conduit 32 is enclosed with insulation. One of the conduits opens to the bottom part of the tank 14 while the other opens into an upper part i.e. an ullage space of the tank 14 and is provided with spraying nozzles. The fuel tank unit 10 comprises at least one liquid fuel conduit 34 extending through the third shell 22 which conduit opens to the bottom part of the second tank 16.

[0041] In the figure 9 there is shown an embodiment of the invention which is otherwise similar to that shown in the figure 1 except that the second tank 16 for the liquid fuel enclosed by a third shell 22 has at least two separate compartments 16.1 , 16.2. The first and the second compartments are both provided with a liquid fuel conduit 34, 35 extending through the third shell 22. A first liquid fuel conduit 34 opens to the bottom part of the first compartment 16.1 of the second tank 16 and a second liquid fuel conduit 35 opens to the bottom part of the second compartment 16.1 of the second tank 16. The first and the second compartments are separated by a fluid tight intermediate wall 17. [0042] According to an embodiment of the invention the tank unit 10 is configured to supply fuel to a so called dual fuel engine where the liquefied gas is used as the main fuel and the liquid fuel, such as a marine diesel oil or light fuel oil, is used as pilot fuel for igniting the main fuel in a combustion chamber of the engine. Now, the first compartment 16.1 is dimensioned to contain the pilot fuel for the engines which consume the liquefied gas as the main fuel. The volume of the first compartment 16.1 of the second tank 16 has a volume which is advantageously 1 - 5% of the volume of the first tank 14 and therefore the volumes correspond substantially the ratio of the consumption of the pilot and the main fuel. The second compartment 16.2 of the second tank 16 may be used for storing liquid fuel for back-up operation when the engine is operated in a so called diesel mode. [0043] While the invention has been described herein by way of examples in connection with what are, at present, considered to be the most preferred embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but is intended to cover various combinations or modifications of its features, and several other applications included within the scope of the invention, as defined in the ap- pended claims. The details mentioned in connection with any embodiment above may be used in connection with another embodiment when such combination is technically feasible.

Claims

1 . A fuel tank unit (10) for storing first liquid, which is liquefied gas fuel, and second liquid, the unit (10) comprising a first tank (14) for liquefied gas fuel and a second tank (16) for the second liquid, characterized in that the first fuel tank (14) is enclosed by a first shell (18) and the first shell (18) is enclosed by a second shell (20) wherein a vacuum heat insulation (24) is arranged between the first shell (18) and the second shell (20), and that the second shell (20) is enclosed at least partially by a third shell (22) wherein the second tank (16) is arranged between the second shell (20) and the third shell (22).

2. A fuel tank unit (10) according to claim 1 , characterized in that the first fuel tank (14) is configured for storing liquefied gas fuel and the second fuel tank (16) is configured for storing liquid fuel, wherein the second fuel tank (16) is arranged between the second shell (20) and the third shell (22).

3. A fuel tank unit (10) according to claim 1 , characterized in that the second shell (20) is completely enclosed by the third shell (22).

4. A fuel tank unit (10) according to claim 1 , characterized in that the fuel tank unit (10) is of elongated form having a length (L), width W), height (H) and longitudinal axis (A) lengthwise the unit (10), and that the second shell (20) has, perpendicular to the longitudinal axis, a circular cross section.

5. A fuel tank unit (10) according to claim 3, characterized in that the third shell (22) has, perpendicular to the longitudinal axis, a polygonal cross section.

6. A fuel tank unit (10) according to claim 3, characterized in that the third shell (22) has, perpendicular to the longitudinal axis, a cross section which is inside a rec- tangle, the sidewalls of which are tangential to the second shell (20).

7. A fuel tank unit (10) according to claim 3, characterized in that the third shell (22) has, perpendicular to the longitudinal axis, a rectangular cross sectional shape.

8. A fuel tank unit (10) according to claim 3, characterized in that at least one wall of the third shell (22) is against to the second shell (20).

9. A fuel tank unit (10) according to claim 3, characterized in that at least two walls of the third shell (22) are against to the second shell (20).

10. A fuel tank unit (10) according to claim 3, characterized in that all of the walls of the third shell (22) are tangential to the second shell (20).

1 1 . A fuel tank unit (10) according to claim 3, characterized in the first and the second shells (18, 20) have, perpendicular to the longitudinal axis, a circular cross section.

12. A fuel tank unit (10) according to claim 1 , characterized in that the heat insulation (24) between the first wall and the second wall is a vacuum insulation (24) con- figured for insulation (24) of cryogenic liquefied gas.

13. A fuel tank unit (10) according to claim 1 , characterized in that the fuel tank unit (10) comprises a fuel conduit extending through the second shell (20) and the third shell (22) and the vacuum insulation (24) to the first tank and that the fuel conduit is enclosed with an insulation (24).

14. A fuel tank unit (10) according to claim 1 , characterized in that the second tank (16) comprises at least two separate compartments (16.1 , 16.2).

15. A fuel tank unit (10) according to claim 1 , characterized in that a first compartment (16.1 ) of the second tank (16) has a volume which is 1 - 5% of the volume of the first tank (14),