Natural gas liquefaction using a more efficient process

摘要

A process for liquefying natural gas in conjunction with producing a liquid stream containing predominantly hydrocarbons heavier than methane is disclosed. In the process, the natural gas stream to be liquefied is partially cooled and divided into first and second streams. The first stream is further cooled to condense substantially all of it, expanded to an intermediate pressure, and then supplied to a distillation column at a first mid-column feed position. The second stream is also expanded to intermediate pressure and is then supplied to the column at a second lower mid-column feed position. A distillation stream is withdrawn from the column below the feed point of the second stream and is cooled to condense at least a part of it, forming a reflux stream and a residual vapour stream. At least a portion of the reflux stream is directed to the distillation column as a top feed. The residual vapour stream is combined with the more volatile vapour distillation stream from the top of the distillation column to form a volatile residue gas fraction containing a major portion of the methane and lighter components. The volatile residue gas fraction is cooled under pressure to condense at least a portion of it and form the condensed liquid stream (LNG).