Patent ID: 7225636

Claim:
A process for producing liquified natural gas comprising: (A) operating a gas cooling loop by (1) contacting a natural gas stream with a return stream of the gas cooling loop to form a combined stream, wherein the natural gas stream comprises methane and heavier hydrocarbons, and the return stream comprises methane, (2) passing the combined stream through a first zone of a heat transfer zone and then to a gas cooling loop first gas/liquid separation zone forming a first separation zone gas stream comprising methane and a gas cooling loop first separation zone liquid stream comprising heavier hydrocarbons, (3) passing the first separation zone gas stream through an expansion zone, then through a second zone of the heat transfer zone, then through the first zone of the heat transfer zone, and then through a compression zone to form the return stream of the gas cooling loop; (B) taking the gas cooling loop first separation zone liquid stream as a distillation zone feed stream, and distilling this distillation zone feed stream into a distilled gas stream comprising methane and a bottom stream comprising heavy hydrocarbons; (C) operating an LNG cooling loop by (1) passing a return stream of the LNG cooling loop to a compression zone to form a compressed stream, (2) passing the compressed stream thru the first zone of the heat transfer zone and then through an expansion zone to form a first expanded stream, (3) combining the first expanded stream with the distilled gas stream from Step (B) to form a combined LNG stream, (4) splitting the combined LNG stream into a first return LNG stream and a first remaining LNG stream, (5) expanding and passing the first return LNG stream thru the first zone of the heat transfer zone and then back to the compression zone, (6) passing the first remaining LNG stream through the second zone of the heat transfer zone and then splitting it into a second return LNG stream and a second remaining LNG stream, (7) expanding and passing the second return LNG stream through the second zone of the heat transfer zone, through the first zone of the heat transfer zone, and then back to the compression zone, (8) passing the second remaining LNG stream through a third zone of the heat transfer zone and then splitting it into a third return LNG stream and a third remaining LNG stream, (9) then expanding and passing the third return LNG stream through the third zone, the second zone and then the first zone of the transfer zone to form the return stream of the LNG cooling loop, and (10) passing the third remaining LNG stream to LNG storage and recovering any LNG vapors as an LNG boiloff stream and combining the boiloff stream with the return stream of the LNG cooling loop, and recovering LNG product from LNG storage as an LNG product stream.