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

An apparatus for the liquefaction of a natural gas stream, comprising:

• a heat exchanger that cools a portion of the natural gas stream to generate a cooled natural gas stream;
• a first separation device configured to remove heavy hydrocarbons from the natural gas stream, combined with the cooled natural gas stream, to thereby generate a separated natural gas stream and a separator bottom stream, wherein the heat exchanger partially condenses the separated natural gas stream to form a partially condensed natural gas stream;
• a second separation device that directly receives the separator bottom stream from the first separation device and separates liquids from the separator bottom stream to form an overhead stream and a stabilized hydrocarbon liquid stream;
• a first cooling unit and a third separation device that cool and separate the overhead stream to form a recycle gas stream;
• a recycle compressor that compresses the recycle gas stream to form a compressed recycle gas stream;
• wherein a first portion of the compressed recycle gas stream is directed through the heat exchanger to form a cooled compressed recycle stream therefrom, the cooled compressed recycle stream being directed to the first separator as a reflux stream, and wherein the separated natural gas stream is used as a coolant in the heat exchanger to thereby generate a pretreated natural gas stream;
• at least one compressor that compresses the pretreated natural gas stream and a second portion of the compressed recycle gas stream to a pressure of at least 1,500 psia, to thereby form a compressed natural gas stream;
• a second cooling unit that cools the compressed natural gas stream to form a cooled compressed natural gas stream;
• at least one work producing natural gas expander that expands the cooled compressed natural gas stream to a pressure that is less than 2,000 psia and no greater than the pressure to which the at least one compressor compresses the pretreated natural gas stream, to thereby form a chilled pretreated gas stream;
• wherein the chilled pretreated gas stream is recycled to the heat exchanger to exchange heat indirectly therein with process streams comprising the portion of the natural gas stream, the separated natural gas stream, and the first portion of the compressed recycle gas stream, thereby generating a warmed refrigerant stream;
• and
• at least one liquefaction unit configured to liquefy the chilled pretreated gas stream.