Heavy Hydrocarbon Removal System for Lean Natural Gas Liquefaction

A method comprising:

• (a) performing a closed-loop compression sequence on a warm first refrigerant stream withdrawn from a warm side of a main heat exchanger, the compression sequence comprising compressing and cooling the warm first refrigerant stream to produce at least one cooled, compressed first refrigerant stream;
• (b) withdrawing a natural gas feed stream from a natural gas feed source at a source pressure;
• (c) introducing the natural gas feed stream into a scrub column at a scrub column pressure, the scrub column having a top section and a bottom section;
• (d) separating the natural gas feed stream in the scrub column into a methane-rich vapor fraction, collected as a first overhead vapor stream at a top end of the scrub column, and a heavy hydrocarbon-enriched fraction, collected as a first bottoms liquid stream at a bottom end of the scrub column;
• (e) withdrawing the first bottoms liquid stream from the scrub column, the first bottoms liquid stream being a heavy hydrocarbon enriched natural gas stream;
• (f) withdrawing the first overhead vapor stream from the scrub column, the first overhead vapor stream being a methane-enriched natural gas stream;
• (g) introducing at a warm end of a warm section of a main heat exchanger, the first overhead vapor stream into a natural gas circuit, and each of the at least one cooled-compressed first refrigerant stream into a refrigerant circuit;
• (h) in at least one of the refrigerant circuits, withdrawing and reducing a pressure of an overhead refrigerant stream to produce a reduced pressure overhead refrigerant stream and introducing the reduced pressure overhead refrigerant stream into a cold side of the main heat exchanger;
• (i) providing indirect heat exchange between the warm side and the cold side of the main heat exchanger;
• (j) producing a product stream from the natural gas circuit at a cold end of the main heat exchanger, the product stream being at least partially liquefied;
• (k) withdrawing a partially condensed natural gas stream from the natural gas circuit at a cold end of the warm section of the main heat exchanger;
• (l) reducing a pressure of the partially condensed natural gas stream to form a reduced pressure partially condensed natural gas stream;
• (m) introducing the reduced pressure partially condensed natural gas stream into a reflux drum at an intermediate natural gas temperature;
• (n) separating the reduced pressure partially condensed natural gas stream into a reflux drum liquid stream and a reflux drum vapor stream;
• (o) introducing the reflux drum vapor stream into the natural gas circuit at a location in the main heat exchanger that is closer to a cold end of the main heat exchanger than the cold end of the warm section;
• (p) increasing a pressure of the reflux drum liquid stream and introducing the reflux drum liquid stream into the top section of the scrub column;
• and
• (q) providing indirect heat exchange between the reflux drum vapor stream and the partially condensed natural gas stream by which the partially condensed natural gas stream is cooled against the reflux drum vapor stream.