Method of producing a gasified hydrocarbon stream; method of liquefying a gaseous hydrocarbon stream; and a cyclic process

1. A method of producing a gasified hydrocarbon stream, at least comprising the steps of:

(a) providing a first liquefied hydrocarbon stream from a first source;

(b) providing a second liquefied hydrocarbon stream from a second source, which second source is at a geographically separate location from the first source and which second liquefied hydrocarbon stream has been liquefied by cooling a gaseous source hydrocarbon stream solely against a first cooled nitrogen-based stream;

(c) gasifying the first and second liquefied hydrocarbon streams to produce a gasified hydrocarbon stream, wherein cooling a gaseous nitrogen-based stream against the gasifying first and second liquefied hydrocarbon streams to provide a second cooled nitrogen-based stream wherein the mass of the second cooled nitrogen-based stream produced using cooling duty released from the first and second liquefied hydrocarbon streams is at least as high as the mass of the first cooled nitrogen-based stream used in step (b), whereby no additional cooling duty is used to cool the gaseous nitrogen-based stream and the gaseous source hydrocarbon stream.

2. The method as claimed in claim 1 , wherein the first and second cooled nitrogen-based streams are liquefied nitrogen-based streams.

3. The method as claimed in claim 1 , wherein the first and second liquefied hydrocarbon streams are combined to form a combined liquefied hydrocarbon stream prior to their gasification.

4. The method as claimed in claim 1 , wherein the mass ratio of the first liquefied hydrocarbon stream to the second liquefied hydrocarbon stream is in the range 2:1 to 8:1.

5. The method as claimed in claim 1 , wherein the first cooled nitrogen-based stream is at least partly gasified at the second source to provide the source of cooling to liquefy the second hydrocarbon stream.

6. The method as claimed in claim 1 , wherein step (a) comprises providing a mass X of the first liquefied hydrocarbon stream; and wherein step (b) comprises providing a mass Y of the second liquefied hydrocarbon stream; and wherein to provide mass Z of the second cooled nitrogen-based stream, wherein the gasifying of the first and second hydrocarbon stream in step (c) produce a mass Z of the second cooled nitrogen-based stream, the mass Z being a sufficient amount to fully liquefy the gaseous source hydrocarbon stream to provide the mass Y of the second liquefied hydrocarbon stream.

7. The method as claimed in claim 1 , wherein the first source of the first liquefied hydrocarbon stream is a first export terminal, and the second source of the second liquefied hydrocarbon stream is a second export terminal.

8. The method as claimed in claim 1 , wherein steps (a), (b) and (c) are performed at an import terminal.

9. The method as claimed in claim 8 , wherein the first liquefied hydrocarbon stream has been transported from the first source to the import terminal by a first vessel, and the second liquefied hydrocarbon stream has been transported from the second source to the import terminal by a second vessel.

10. The method as claimed in claim 9 , wherein the second cooled nitrogen-based stream is transported from the import terminal to the second source by the second vessel.

11. The method as claimed in claim 1 , wherein the first and second liquefied hydrocarbon streams are liquefied natural gas streams.

12. A method of liquefying a gaseous hydrocarbon stream, at least comprising the steps of:

(a) providing a second cooled nitrogen-based stream;

(b) liquefying a hydrocarbon stream solely by cooling against the second cooled nitrogen-based stream to provide a liquefied hydrocarbon stream; wherein the second nitrogen-based stream has been obtained from a gaseous nitrogen-based stream that has been cooled against a first liquefied hydrocarbon stream provided from a first source and against a second liquefied hydrocarbon stream provided from a second source, during which cooling the first and second liquefied hydrocarbon streams have been gasified, and whereby no additional cooling is used to cool the gaseous nitrogen-based stream, which second source is at a geographically separate location from the first source and which second liquefied hydrocarbon stream has been liquefied by cooling solely against a first cooled nitrogen-based stream, wherein the mass of the first cooled nitrogen-based stream used in step (b) is at most equal to the mass of the second cooled nitrogen-based stream, and no additional cooling is used to liquefy the first cooled nitrogen-based stream.

13. The method as claimed in claim 12 , wherein the first and second cooled nitrogen-based streams are liquefied nitrogen-based streams.

14. The method as claimed in claim 12 , wherein the gaseous hydrocarbon stream is liquefied to provide the second liquefied hydrocarbon stream of step (b).

15. A cyclic process wherein cooling and re-warming a nitrogen-based stream, and wherein liquefying and regasifying a hydrocarbon stream, comprising the steps of:

(a) at a first export location, liquefying a first gaseous hydrocarbon stream to produce a first liquefied hydrocarbon stream;

(b) at a second export location, being geographically separate from the first export location, importing a cooled nitrogen-based stream which has been produced at an import location in step (e);

(c) at the second export location, liquefying a second gaseous hydrocarbon stream by cooling solely against the cooled nitrogen-based stream to produce a second liquefied hydrocarbon stream, wherein no additional cooling duty is used to liquefy the second gaseous hydrocarbon stream;

(d) at the import location, importing the first and the second liquefied hydrocarbon streams which have been produced at the first and second export locations in steps (a) and (c) respectively;

(e) at the import location, cooling a nitrogen-based gaseous stream against the first and second liquefied hydrocarbon streams imported in step (d), thereby producing the cooled nitrogen-based stream and a gasified hydrocarbon stream, whereby no additional cooling duty is used to cool the nitrogen-based gaseous stream; and

(f) transporting the cooled nitrogen-based stream to the second export location, wherein the mass of the cooled nitrogen-based stream produced in (e) using cooling duty released from the first and second liquefied hydrocarbon streams is at least as high as the mass of the cooled nitrogen-based stream used in step (c).

16. The method as claimed in claim 12 , wherein the mass ratio of the first liquefied hydrocarbon stream to the second liquefied hydrocarbon stream is in the range 2:1 to 8:1.

17. The method as claimed in claim 12 , wherein said liquefying of said hydrocarbon stream in step (b) is performed at the second source, and wherein the first cooled nitrogen-based stream has been produced at an import terminal and transported from the import terminal to the second source by a second vessel, wherein liquefied hydrocarbon stream provided in step (b) is transported to the import terminal by the second vessel.