WO2016016647A1

WO2016016647A1 - Lng bunker vessel

Info

Publication number: WO2016016647A1
Application number: PCT/GB2015/052194
Authority: WO
Inventors: Andrew Scott; John Alfred ELTRINGHAM
Original assignee: Liquid Gas Equipment Limited; Bernhard Schulte Shipmanagement (Uk) Limited
Priority date: 2014-07-30
Filing date: 2015-07-30
Publication date: 2016-02-04
Also published as: GB201413486D0; GB2535425A; EP3175165A1; CN107076364A; JP2017523084A; KR20170069999A

Abstract

An LNG bunker vessel having: one or more LNG tanks, a first pipeline able to transfer liquefied natural gas (LNG) from one or more of the LNG tanks on the LNG bunker vessel to one or more off-vessel LNG receiver tanks, one or more natural gas compressors on the LNG bunker vessel able to compress natural gas and provide compressed natural gas (CNG), a second pipeline able to transfer natural gas from the one or more off-vessel LNG receiver tanks to the one or more natural gas compressors on the LNG bunker vessel; and one or more CNG storage tank(s) on the LNG bunker vessel to store CNG provided by the one or more natural gas compressors as a fuel source. In this way, the apparatus and operation for transforming natural gas from the off- vessel LNG receiver tank(s) into a suitable fuel source as CNG is provided on the LNG bunker vessel, and does not require ancillary equipment and operation at the location or site of every off-vessel LNG receiver tank.

Description

LNG Bunker Vessel

The present invention relates to a liquefied natural gas (LNG) bunker vessel including a compressed natural gas (CNG) storage tank or tanks, and a process for providing CNG as a fuel source on an LNG bunker vessel.

Liquefied natural gas (LNG) is natural gas, predominately methane, that has been converted to liquid form for ease of storage and/or transport. Natural gas is being used increasingly as a fuel source, especially commercially, and the most efficient form of transporting it from its source to a major supply hub for users is in the form of LNG, frequently by LNG cargo vessels.

An increasing use of LNG as a fuel source is in various vessels of all sizes, such as ferries. LNG can be supplied to such vessels using LNG bunker vessels, which are generally smaller than LNG cargo vessels, and include one or more LNG tanks. LNG bunker vessels are able to provide the LNG directly as a fuel source to such LNG 'receivers', generally either being the fuel tanks of such vessels, or on-shore fuel tanks used to refuel such vessels.

LNG bunker vessels are known in the art, and may become an increasingly important means of transporting LNG from major hubs to smaller fuel tanks as stricter environmental regulations are introduced. However, as LNG is transferred from a tank of an LNG bunker vessel to the fuel tank of another vessel or to an on- shore fuel tank, gas in the receiving tank is displaced (hereinafter termed 'displaced gas'), and boil-off gas (BOG) and/or flash gas are typically created. Boil-off gas is simply that portion of the LNG that naturally evaporates as part of the transfer. Flash gas is particularly created where conditions in a receiving tank are not optimal (usually because it is too warm or at too low a pressure), creating rapid evaporation of some LNG. BOG, displaced gas and flash gas are all still forms of 'natural gas'. Some of the natural gas created in this way can be returned into the LNG tank(s) of the LNG bunker vessel to at least partially help balance or equalise the pressure change in the LNG tank(s) as the LNG is transferred from the LNG tank(s) to the receiver tank(s). However, there are many occasions where there is an excess amount of natural gas created during the transfer. Currently, such excess natural gas is either simply vented to atmosphere, or combusted.

It is an object of the present invention to recover excess natural gas during such an LNG transfer for use or reuse as a fuel source.

Thus, according to one aspect of the present invention, there is provided an LNG bunker vessel having:

one or more LNG tanks,

a first pipeline able to transfer liquefied natural gas (LNG) from one or more of the LNG tanks on the LNG bunker vessel to one or more off-vessel LNG receiver tanks, one or more natural gas compressors on the LNG bunker vessel able to compress natural gas and provide compressed natural gas (CNG),

a second pipeline able to transfer natural gas from the one or more off-vessel LNG receiver tanks to the one or more natural gas compressors on the LNG bunker vessel; and

one or more CNG storage tanks on the LNG bunker vessel to store CNG provided by the one or more natural gas compressors as a fuel source.

In this way, the apparatus and operation for transforming natural gas from the off- vessel LNG receiver tank(s) into a suitable fuel source as CNG is provided on the LNG bunker vessel, and does not require ancillary equipment and operation at the location or site of every off-vessel LNG receiver tank.

The nature, size, shape and design of LNG bunker vessels are known in the art. Generally, an LNG bunker vessel comprises one or more LNG tanks, typically two or three tanks, and can be designed to carry hundreds or thousands of litres or cubic metres (e.g. 6000m³) of LNG, generally to supply LNG as a fuel source to one or more off-vessel LNG receiver tanks either sequentially or simultaneously. The storage requirements, process and conditions of the LNG on an LNG bunker vessel is known to those skilled in the art. The LNG bunker vessel comprises a first pipeline able to transfer LNG from an LNG tank or more than one LNG tank on the LNG bunker vessel, to one or more off-vessel LNG receiver tanks.

The term "off-vessel LNG receiver tank" as used herein includes any tank intended to store and provide LNG as a fuel source to a vessel or other means of transport or industrial factory or premises etc. Thus, the off-vessel LNG receiver tankfs) may be on-shore or off-shore. A typical example is the fuel tank of a vessel such as a passenger ferry or a commercial ferry. Other examples include other sea-going vessels such as cruise liners, barges, and commercial transport vessels. On-shore users include factories, etc. The off-vessel LNG receiver tankfs) may also be a fuel depot or hub for other, usually smaller, users of LNG.

The size, design and use of the off-vessel LNG receiver tank(s) is not limiting to the present invention, subject only to such a receiver tank not being on the LNG bunker vessel, and hence 'off-vessel'. Off vessel' includes on-shore, off-shore or a combination of both.

Optionally, one off-vessel LNG receiver tank is the fuel tank(s) of a vessel. The nature of the first pipeline, which is able to transfer LNG from the LNG tank(s) on the LNG bunker vessel to the off-vessel LNG receiver tank(s), is also known in the art and is not further described herein. The first pipeline may comprise one or more pipelines working in tandem or in an otherwise coordinated manner to transfer LNG from the LNG tankfs) on the LNG bunker vessel to the off-vessel LNG receiver tankfs). In use, the LNG bunker vessel is connected via at least the first and second pipelines to the off-vessel LNG receiver tank(s). Optionally, the LNG bunker vessel is secured to the support or base for the off-vessel LNG receiver tank(s). As LNG is passed into the off-vessel LNG receiver tank(s), BOG, displaced gas or flash gas, or any combination of same, are usually created. Thus, optionally, the natural gas from the one or more off-vessel LNG receiver tanks comprises one or more of the group comprising: boil-off gas, displaced gas, and flash gas. In the present invention, the second pipeline is provided to transfer such natural gas from the off-vessel LNG receiver tank(s) to one or more natural gas compressors on the LNG bunker vessel. The nature, design and shape of the second pipeline is not limiting, and is generally able to transfer natural gas in a manner known in the art. The second pipeline may also comprise one or more pipelines working in tandem or in an otherwise coordinated manner.

In one embodiment of the present invention, the second pipeline is able to transfer natural gas directly from the off-vessel LNG receiver tank(s) to the natural gas compressor(s) on the LNG bunker vessel. That is, without the diversion of the natural gas to one or more other significant apparatus or units or the like.

In another embodiment of the present invention, the second pipeline is able to transfer natural gas indirectly from the off-vessel LNG receiver tank(s) to the natural gas compressor(s) on the LNG bunker vessel. That is, with the diversion of the natural gas to one or more other apparatus or units or the like, such as one or more holding tanks, including the one or more LNG tanks on the LNG bunker vessel.

Optionally, the second pipeline is partly, wholly or substantially located alongside the first pipeline between the LNG bunker vessel and the off-vessel LNG receiver tank(s). Natural gas compressors are known in the art, and are generally intended to compress natural gas to a higher pressure. Typically this can be from ambient pressure, or a low pressure of a few bars, to a pressure greater than 100 bar, optionally greater than 200 bar, and frequently in the range 240 to 260 bar, such as 250 bar.

Compressed natural gas (CNG) is generally methane stored at a high pressure, and it is being increasingly used for transport in place of gasoline. Typically, CNG combustion produces fewer undesirable gases than gasoline and similar fuels, and CNG is typically safer than other fuels in the event of a spill (especially because natural gas is lighter than air and disperses quickly when released). An increasing number of cars and public transport vehicles such as buses are now being fuelled with CNG. The CNG storage tank(s) on the LNG bunker vessel are able to receive the CNG created by the natural gas compressor(s), and store it as a fuel source. The or each CNG storage tank may comprise one or more tanks or bunkers or compartments or storage areas or combination of same, optionally with the inclusion of internal materials able to store CNG at a greater density.

In one embodiment of the present invention, the CNG is a fuel source for the LNG bunker vessel. Thus, there can be provided a third pipeline between the CNG storage tank(s) and either to the engine(s) or a part thereof of the LNG bunker vessel, or to any separate fuel tank(s) of the LNG bunker vessel, or to both, optionally with the required intermediate apparatus or provisions for providing the CNG as the correct fuel, generally in the form of lower pressure gas, to the or each relevant engine.

Thus, according to another embodiment of the present invention, the LNG bunker vessel includes a pressure let-down system between the CNG storage tank(s) and the engine(s) of the LNG bunker vessel, able to provide the CNG as the fuel for the or each engine from the third pipeline. In particular, where the LNG bunker vessel itself uses the CNG from the CNG storage tank, there is an increased meeting of zero methane emissions targets now being presented to users of LNG bunker vessels.

Further, and BOG created during the operation of the LNG bunker vessel when loaded with LNG in its LNG tank(s) can also be compressed to CNG using the same apparatus, and then used as a fuel source, in particular in the engine(s) of the LNG bunker vessel.

According to an alternative embodiment of the present invention, the CNG in or related to the CNG storage tank(s) can be transferred to another off-vessel tank or supply pipeline, either through a transfer pipeline or by relocation of the CNG storage tank(s) (to be replaced by another or empty CNG storage tank(s)), and for use as a fuel source for one or more other motors or engines separate from the LNG bunker vessel. Any such off-vessel tank or supply pipeline may be on-shore or still off-shore, preferably on-shore.

The present invention is not limited by the ultimate use or user of the C G created by the one or more natural gas compressors on the LNG bunker vessel.

According to a second aspect of the present invention, there is provided a process for providing CNG as a fuel source on an LNG bunker vessel, comprising at least the steps of:

(i) providing an LNG bunker vessel having one or more LNG tanks, one or more natural gas compressors, and one or more CNG storage tanks;

(if) transferring liquefied natural gas (LNG) from one or more of the LNG tanks on the LNG bunker vessel to one or more off-vessel LNG receiver tanks;

(iii) transferring natural gas from one or more of the off-vessel LNG receiver tanks to the LNG bunker vessel; (iv) compressing the natural gas in the one or more natural gas compressors to provide compressed natural gas (CNG);

(v) storing the CNG in one or more of the CNG storage tanks on the LNG bunker vessel for use as a fuel source.

According to one embodiment of the present invention, the process of the present invention further comprises:

(vi) transferring the CNG in one or more of the CNG storage tanks to one or more engines of the LNG bunker vessel.

According to an alternative embodiment of the present invention, the process of the present invention further comprises:

(vi] transferring the CNG in one or more of the CNG storage tanks to one or more off-vessel tanks or supply pipelines for use as a fuel source.

The natural gas being transferred in step (iii) comprises boil-off gas, displaced gas, or flash gas, or any combination of same.

The transfer of the natural gas from one or more of the off-vessel LNG receiver tanks to the one or more natural gas compressors may be carried out directly or indirectly as discussed hereinabove.

According to a third aspect of the present invention, there is provided a system for providing CNG as a fuel source on an LNG bunker vessel, the system comprising an LNG bunker vessel having one or more LNG tanks, a first pipeline between one or more of the LNG tanks and one or more off-vessel LNG receiver tanks, the transfer of LNG from the LNG bunker vessel to the off-vessel receiver tank(s) via the first pipeline, the displacement, creation, or combination of both, of natural gas in the off- vessel receiver tank(s) due to the LNG transfer, the transfer of the so-formed natural gas from the off-vessel receiver tank(s) via a second pipeline to one or more natural gas compressors on the LNG bunker vessel, the creation of compressed natural gas (CNG) by the one or more natural gas compressors, and the passing of the so-formed CNG into one or more CNG storage tanks on the LNG bunker vessel for use as a fuel source.

Optionally, the off-vessel receiver tank(s) is on a separate vessel. Preferably, the off- vessel receiver tank(s) is the fuel tank of the separate vessel.

Optionally, the system further comprises passing the CNG in the CNG storage tank(s) to the engine(s) and/or any separate fuel tank(s) of the LNG bunker vessel as a fuel source for the engine(s) of the LNG bunker vessel.

Optionally, the system further comprises transferring the CNG to one or more off- vessel tanks or supply pipelines for use as a fuel source.

As used herein, the term "system" is the assembly or arrangement of the LNG bunker vessel and one or more connected off-vessel LNG receiver tanks. The transfer of the so-formed natural gas from the off-vessel receiver tank(s] via a second pipeline to one or more natural gas compressors on the LNG bunker vessel may be carried out directly or indirectly as discussed hereinabove. According to a further aspect of the invention, there is provided a method of integratively designing a vessel, such as an LNG bunker vessel, comprising the steps of:

selecting one or more LNG tanks for use within the LNG bunker vessel;

selecting a first pipeline for the operational transfer of LNG from the one or more LNG tanks to one or more off-vessel LNG receiver tanks;

selecting one or more natural gas compressors to compress natural gas and to provide CNG;

selecting a second pipeline for the operational transfer of natural gas from one or more off-vessel LNG receiver tanks to the one or more natural gas compressors; selecting one or more CNG storage tanks on the LNG bunker vessel to store CNG provided by the one or more natural gas compressors; and selecting a third pipeline for operational transfer of CNG from the one of more CNG storage tanks for use as a fuel source for the operation and propulsion of the LNG vessel. According to a still further aspect of the invention, there is provided a method of designing an interactive transfer of LNG between a vessel, such as an LNG bunker vessel, and a separate off-vessel storage, such as another vessel or a land-based facility, comprising the steps of:

designing an LNG vessel, including

selecting one or more LNG tanks for use within the LNG bunker vessel;

selecting a first pipeline for fluid communication with and for operational transfer of LNG from the one or more LNG tanks to LNG receiver tanks within off- vessel storage;

selecting a second pipeline for fluid communication with and for operational transfer of natural gas from the off-vessel LNG receiver tank(s) to the one or more natural gas compressors;

selecting one or more CNG storage tanks to store CNG provided by the one or more natural gas compressors; and

selecting a third pipeline for operational transfer of CNG from the one of more CNG storage tanks for use as a fuel source for the operation and propulsion of the LNG bunker vessel. According to a still further aspect of the invention, there is provided a method of designing a process for providing CNG as a fuel source on a vessel, such as an LNG bunker vessel, comprising the same or similar steps as described herein.

The designing methods as discussed herein may incorporate computer aided processes for incorporating the relevant operational equipment and controls into the overall vessel construction and may incorporate relevant cost, capacity of operation parameters into the methodology and design. The methods described herein may be encoded onto media that is suitable for being read and processed on a computer. For example, code to carry out the methods described herein may be encoded onto a magnetic or optical media which can be read by and copied to a personal or mainframe computer. The methods may then be carried out by a design engineer using such a personal or mainframe computer.

Certain features of the present invention and its method of design may be described in terms of a set of numerical upper limits and a set of numerical lower limits. It should be appreciated that any ranges formed by any combination of such limits are contemplated to fall within the scope of the invention. Further the overall design is contemplated to include the selection of additional structures for use with the combination herein specifically defined. The various structures operational parameters may be selected for a limited or fixed basis or selected for flexible or multiple operational use within the vessel. Hence, it is intended that the method of design covers alternatives, modifications, and equivalents with respect to the overall design of the vessel and any off-vessel that are included within the spirit and scope of the invention. Embodiments and an example of the present invention will now be described by way of example only and with reference to the accompanying schematic drawings, data and graphs in which:

Figure 1 is a side schematic view of an LNG bunker vessel according to embodiments of the present invention;

Figure 2 is a side schematic view of another embodiment of the present invention; Figure 3 comprises example data; and

Figure 4 comprises CNG tank pressure and CNG feed to engine graphs. Referring to the drawings, Figure 1 shows an LNG bunker vessel 2 having two LNG tanks 4. As mentioned hereinbefore, LNG bunker vessels are known in the art, and may comprise one or more LNG tanks in order to provide, generally within a supply chain, LNG as a fuel to one or more on-shore or off-shore tanks or vessels, means of transport, factories etc., or fuel hubs therefor.

By way of example only, an LNG bunker vessel could be loaded with LNG at or near a major LNG hub in a harbour or storage area such as the Port of Rotterdam, and then travel to one or more, usually at least two or three, destinations, to supply the LNG as a fuel source, usually a marine fuel source, to one or more other vessels or fuel sources or hubs. Figure 1 shows a second vessel 6 having a fuel tank 8 (usually located on or within the vessel) for an engine 9 of the second vessel 6. Thus, the fuel tank 8 of the second vessel 6 can be designated as an "off-vessel LNG receiver tank 8". The second vessel 6 may have more than one such fuel tank. Figure 1 shows a first pipeline 10 able to transfer liquefied natural gas (LNG) 12 from an LNG tank 4 on the LNG bunker vessel 2 to the off-vessel LNG receiver tank 8. This is generally carried out in a manner known in the art, and the process, and process conditions and parameters, will be known to the person skilled in the art. As the LNG reaches the off-vessel LNG receiver tank 8, gas still in the LNG receiver tank 8 will be displaced as 'displaced gas', and either boil-off gas (BOG), or flash gas, or both may also be created in a manner known in the art. The collection and/or any combination of these three gases that derive from the LNG receiver tank 8 during its filling is hereinafter generally termed 'natural gas'.

Conventionally, whilst some of this natural gas is used to help balance or fully or partly equalise the pressure in the LNG tank 4 during the LNG transfer, any excess natural gas is currently typically either vented to atmosphere, or sent to a gas combustion unit. Environmentally, this is increasingly not preferred or desired.

Figure 1 shows the LNG bunker vessel 2 having one or more natural gas compressors 15 located on the LNG bunker vessel 2, and a second pipeline 14 able to transfer natural gas from the off-vessel LNG receiver tank 8 directly to the one or more natural gas compressors 15. The process and process parameters and conditions for the transfer of natural gas along the second pipeline are not further described, and will be known to those skilled in the art.

Natural gas compressors are also known in the art, and generally increase the pressure of natural gas by a significant multiple, generally into a form known as compressed natural gas (CNG] having a pressure (at ambient temperature] of several bar, or tens of MPa, typically greater than 100 bar, greater than 200 bar, and optionally at or approximately 250 bar.

Figure 1 shows a CNG storage tank 16 (optionally being more than one CNG tank] on the LNG bunker vessel 2 to store the so-formed CNG from the one or more natural gas compressors 15 as a fuel source.

Figure 1 shows a third pipeline 18 able to pass the CNG from the CNG storage tank 16 directly to an engine or engine control unit, apparatus, etc. 20 of the LNG bunker vessel 2, generally via one or more required apparatus such as one or more pressure let-down valves 22, optionally being a pressure let-down system (not shown].

Figure 1 shows the ability of the present invention to provide a means of recovery of natural gas from the off-vessel LNG receiver tank into a useful CNG fuel source, and in particular as a fuel source for the LNG bunker vessel itself. In this way, the LNG bunker vessel is able to increasingly meet a zero methane emissions target by its reuse of the natural gas created by the transfer of its LNG to the off-vessel LNG receiver tank.

Figure 1 also shows a fourth pipeline 24 between the LNG tank 4 and the second pipeline 14 useable for two purposes. Firstly, it can transfer BOG created in the LNG tank 4 into the second pipeline 14, to also be compressed by the one or more natural gas compressors 15 into CNG as a fuel source in the CNG storage tank 16. Secondly, it can be used to transfer any portion of the natural gas provided by the off-vessel LNG receiver tank 8 during the LNG transfer to at least partially help balance or equalise the pressure in the LNG tank 4 during the transfer of LNG 12 out of the same tank 4. In a first alternative embodiment, Figure 1 also shows the transfer of the natural gas from the off-vessel LNG receiver tank 8 indirectly to the one or more natural gas compressors 15. By way of example only, the indirect transfer can be carried out initially along the second pipeline 14, and then along the fourth pipeline 24 back into one or more of the LNG tanks 4, and then via a fifth pipeline 26 between the LNG tank(s) 4 and the natural gas compressor(s) 15.

Pipework for the involvement of the other LNG tank 4 shown in Figure 1 is not shown for clarity, but may be the same as that shown. Figure 2 shows a second embodiment of the present invention. In the second embodiment the LNG bunker vessel 2 comprises LNG tanks 4, and a first pipeline 10 able to transfer liquefied natural gas 12 from an LNG tank 4 to an on-shore tank 30 (comprising one or more tanks), which tank 30 is also an off-vessel LNG receiver tank. The on-shore tank 30 may be the same type of tank as the fuel tank 8 of the second vessel 6 shown in Figure 1. It may also be a fuel depot or fuel hub for other (typically on-shore or land-based) users such as commercial vehicles.

The on-shore tank 30 will displace gas/create boil-off gas, flash gas or both, in the same way as Figure 1 during an LNG transfer thereinto. This so-formed natural gas that can be transferred via the second pipeline 14 extending from the on-shore tank 30 to one or more natural gas compressors 15 on the LNG bunker vessel 2, (either directly, or indirectly via the fourth pipeline 24 back into one or more of the LNG tanks 4, and then via a fifth pipeline 26). The CNG created thereby can be stored in a downstream CNG storage tank(s) 16.

Figure 2 also shows a sixth pipeline 32 able to transfer CNG in or associated with the CNG storage tank 16 for use as a fuel source or supply pipeline (not shown) in another location. This transfer could be directly or indirectly to an off-vessel fuel source [not shown). The provision of CNG via the sixth pipeline 32 may be in addition to or as an alternative to the supply of CNG to the engine 20 of the LNG bunker vessel 2.

Figures 3 and 4 are data and graphs for an example voyage of an LNG bunker vessel according to the present invention having a natural gas compressor(s) and CNG storage tank(s) thereon. The LNG bunker vessel has a total LNG capacity of 6803 m³ in two LNG tanks to store LNG at -161°C.

Starting at "0.0" hours, there is a 10-hour 'loading' period during which the LNG bunker vessel is loaded with approximately 5900 m³ of LNG at a suitable hub, terminal or port. At this time, the CNG storage tank is effectively 'empty', and thus there is a minimum CNG tank pressure, and a 'zero' CNG feed therefrom to the engine of the LNG bunker vessel.

After a 2-hour period of 'outboard loaded pilotage' from the hub, the loaded LNG bunker vessel then has a 'loaded transit' journey of 386 nautical miles over a time of 32.17 hours. During the loaded transit journey, BOG from the LNG tanks is compressed to provide CNG: hence filling the CNG storage tank and thereby increasing the CNG tank pressure. This CNG is used as a fuel source, for example halfway along the transit loaded period, to feed the engine of the LNG bunker vessel.

After an 'inbound loaded pilotage' of 2 hours, and a cooldown period of 1 hour, the LNG in the LNG tanks is discharged over a period of 19.67 hours to one or more off- vessel LNG receiver tanks having a total volume of 6400 m³ at an average cargo transfer rate of 300 m³/h. In this example, the total cargo transferred is 5900 m³. During the transfer, displaced gas, BOG and possibly flash gas is created, which is provided to the one or more natural gas compressors on the LNG bunker vessel. This creates CNG to be stored in the CNG storage tank, which therefore increases the CNG tank pressure in the CNG storage tank over the discharge period, until the end of the discharge.

The LNG vessel is then ready to return to its loading hub facility, starting with a 2- hour Outbound ballast pilotage', followed by a ballast transit journey or period of 32.17 hours before a final 2-hour 'inbound ballast pilotage'.

During the ballast transit journey, the CNG in the CNG storage tank is provided to the engine of the LNG bunker vessel, optionally at a constant flow rate as shown in Figure 4 lower, such that the pressure in the CNG storage tank correspondingly decreases during the ballast transit period back down to its minimum, prior to the next loading and transit cycle.

Thus, in the overall voyage and operation, the LNG bunker vessel has used the CNG created as a fuel source, and the present invention provides a system on or with the LNG bunker vessel to better meet zero methane emissions targets for the LNG bunker vessel by recovery of the natural gas created over the whole voyage.

Claims

1. An LNG bunker vessel having: one or more LNG tanks,

2. An LNG bunker vessel as claimed in Claim 1 wherein the one or more off- vessel LNG receiver tanks are on-shore.

3. An LNG bunker vessel as claimed in Claim 1 wherein the one or more off- vessel LNG receiver tanks are off-shore.

4. An LNG bunker vessel as claimed in Claim 3 wherein the or each off-vessel LNG receiver tank is a fuel tank of a vessel.

5. An LNG bunker vessel as claimed in any one of the preceding claims wherein the natural gas from the one or more off-vessel LNG receiver tanks comprises one or more of the group comprising: displaced gas, boil-off gas and flash gas.

6. An LNG bunker vessel as claimed in any one of the preceding claims wherein the CNG is a fuel source for the LNG bunker vessel.

7. An LNG bunker vessel as claimed in claim 6 including a pressure let-down system between the CNG storage tank(s) and the engine(s) of the LNG bunker vessel.

8. An LNG bunker vessel as claimed in any one of the preceding claims wherein the CNG is transferred to one or more off-vessel tanks or supply pipelines.

9. An LNG bunker vessel as claimed in any one of the preceding claims wherein the second pipeline is able to transfer natural gas indirectly from the off-vessel LNG receiver tank(s) to the natural gas compressor(s) via the one or more LNG tanks on the LNG bunker vessel.

10. A process for providing CNG as a fuel source on an LNG bunker vessel, comprising at least the steps of:

(ii) transferring liquefied natural gas (LNG) from one or more of the LNG tanks on the LNG bunker vessel to one or more of the off-vessel LNG receiver tanks;

(iii) transferring natural gas from one or more of the off-vessel LNG receiver tanks to the LNG bunker vessel;

(iv) compressing the natural gas in the one or more natural gas compressors to provide compressed natural gas (CNG]; and

11. A process as claimed in claim 10 further comprising:

12. A process as claimed in claim 10 further comprising: (vi) transferring the CNG in one or more of the CNG storage tanks to one or more off-vessel tanks or supply pipelines for use as a fuel source.

13. A system for providing compressed natural gas (CNG) as a fuel source on an LNG bunker vessel, the system comprising an LNG bunker vessel having one or more LNG tanks, a first pipeline between one or more of the LNG tanks and one or more off-vessel LNG receiver tanks, the transfer of liquefied natural gas (LNG) from the LNG bunker vessel to the one or more off-vessel receiver tanks via the first pipeline, the displacement, creation, or both, of natural gas in the one or more off- vessel receiver tanks due to the LNG transfer, the transfer of the so-formed natural gas from the one or more off-vessel receiver tanks via a second pipeline to one or more natural gas compressors on the LNG bunker vessel, the creation of CNG by the one or more natural gas compressors, and the passing of the so-formed CNG into one or more CNG storage tanks on the LNG bunker vessel for use as a fuel source.

14. A system as claimed in claim 13 wherein the one or more off-vessel receiver tanks are on a separate vessel.

15. A system as claimed in claim 13 or claim 14 wherein one or more of the off- vessel receiver tanks is a fuel tank of the separate vessel.

16. A system as claimed in any one of claims 13 to 15 wherein the CNG is a fuel source for the LNG bunker vessel.

17. A system as claimed in any one of claims 13 to 16 wherein the CNG is transferred to one or more off-vessel tanks or supply pipelines for use as a fuel source.