Pretreatment and pre-cooling of natural gas by high pressure compression and expansion

An apparatus for the liquefaction of natural gas, comprising:

• a first separation device configured to remove heavy hydrocarbons from a natural gas stream to thereby generate a separated natural gas stream;
• a first heat exchanger that partially condenses the separated natural gas stream, thereby forming a partially condensed natural gas stream;
• a second separation device that separates liquids from the partially condensed natural gas stream to thereby generate a liquids stream and a pretreated natural gas stream;
• at least two serially arranged compressors configured to compress the pretreated natural gas stream to a pressure greater than 1,500 psia, thereby forming a compressed natural gas stream;
• a cooling element configured to cool the compressed natural gas stream, thereby forming a cooled compressed natural gas stream;
• at least one work-producing expander configured to expand the cooled compressed natural gas stream to a pressure which is less than 2,000 psia and is no greater than the pressure to which the at least two serially arranged compressors compress the pretreated natural gas stream, to thereby form a chilled natural gas stream;
• wherein the chilled natural gas stream is separated into a refrigerant stream and a non-refrigerant stream, and wherein the refrigerant stream is warmed through heat exchange in the first heat exchanger with one or more of the natural gas stream, the separated natural gas stream, the partially condensed natural gas stream, the pretreated natural gas stream, and the liquids stream, thereby generating a warmed refrigerant stream;
• and
• at least one liquefaction train configured to liquefy the warmed refrigerant stream and the non-refrigerant stream,
• wherein, prior to compressing the pretreated natural gas stream, the pretreated natural gas stream is directed to the first heat exchanger to be warmed through heat exchange with the separated natural gas stream therein.