Separation of Heavy Hydrocarbons and NGLs from Natural Gas in Integration with Liquefaction of Natural Gas

摘要

Described herein is a method of and system for fractionating and liquefying a natural gas feed stream. The natural gas is first fractionated in a scrub column. The overhead vapor from the scrub column is cooled, condensed and divided to form a first, a second and at least one further stream of liquefied first overhead. The first stream of liquefied first overhead is returned to the scrub column as a reflux stream. The second stream of liquefied first overhead forms an LNG product. The further stream of liquefied first overhead is used to provide or generate reflux for a de-methanizer column used to fractionate the bottoms liquid from the scrub column.

主权项

1. A method of fractionating and liquefying a natural gas feed stream, the method comprising:
(a) introducing the natural gas feed stream into a scrub column in which the natural gas feed stream is separated into a methane-rich vapor fraction collected as a first overhead vapor at the top of the scrub column, and a liquid fraction, enriched in hydrocarbons heavier than methane, collected as a first bottoms liquid at the bottom of the scrub column; (b) withdrawing a stream of first overhead vapor from the top of the scrub column, and cooling, condensing and dividing said stream to form a first stream of liquefied first overhead, second stream of liquefied first overhead, and at least one further stream of liquefied first overhead; (c) returning the first stream of liquefied first overhead to the scrub column as a reflux stream introduced into the top the scrub column, thereby providing reflux for the scrub column; (d) forming a liquefied natural gas (LNG) product stream from the second stream of liquefied first overhead; (e) withdrawing a stream of first bottoms liquid from the bottom of the scrub column, and introducing said stream into a de-methanizer column in which the stream of first bottoms liquid is separated into a methane-rich vapor fraction collected as a second overhead vapor at the top of the de-methanizer column, and a liquid fraction, enriched in hydrocarbons heavier than methane, collected as a second bottoms liquid at the bottom of the de-methanizer column; and (f) providing reflux to the de-methanizer column by:
(1) introducing one of said further streams of liquefied first overhead as a reflux stream into the top of the de-methanizer column; and/or(2) condensing, by indirect heat exchange with one of said further streams of liquefied first overhead, a portion of the second overhead vapor to form a stream of liquefied second overhead that is reintroduced as a reflux stream into the top the de-methanizer column.