Patent ID: 7415840

Claim:
A method of liquefying a natural gas stream in an LNG facility, said method comprising: (a) cooling at least a portion of said natural gas stream in an upstream refrigeration cycle via indirect heat exchange with an upstream refrigerant to thereby provide a cooled natural gas stream; (b) separating at least a portion of said cooled natural gas stream into a predominantly methane vapor overhead fraction and a predominantly liquid bottoms fraction in a first distillation column; (c) cooling at least a portion of said predominantly methane vapor overhead fraction in a second refrigeration cycle via indirect heat exchange with a second refrigerant to thereby provide a cooled predominantly methane stream; (d) passing at least a portion of said cooled predominantly methane stream through a first expander to generate work and to thereby provide a first expanded predominantly methane stream; (e) separating at least a portion of said first expanded predominantly methane stream in a first separation vessel to thereby provide a first vapor stream and a first liquid stream; (f) (g) converting at least a portion of the work generated by said first expander into electricity; and (h) using the electricity generated in step (g) to power a first compressor, wherein said first compressor is used to compress at least a portion of said first vapor stream.