NATURAL GAS LIQUEFACTIONA 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 A distillation stream is withdrawn from the column below the feed point of the second stream and is cooled to condense at least a part of it, forming a reflux stream. At least a portion of the reflux stream is directed to the distillation column as its top feed. The bottom product from this distillation column preferentially contains the majority of any hydrocarbons heavier than methane that would otherwise reduce the purity of the liquefied natural gas. The residual gas stream from the distillation column is compressed to a higher intermediate pressure, cooled under pressure to condense it, and then expanded to low pressure to form the liquefied natural gas stream.In a process for liquefying a natural gas stream containing methane and heavier hydrocarbon components wherein (a) said natural gas stream is cooled under pressure to condense at least a portion of it and form a condensed sfream; and (b) said condensed sfream is expanded to lower pressure to form said liquefied natural gas sfream; the improvement wherein (1) said natural gas stream is treated in one or more cooling steps; (2) said cooled natural gas sfream is divided into at least, a first sfream and a second stream; (3) said first stream is cooled to condense substantially all of it and thereafter expanded to an intermediate pressure; (4) said second stream is expanded to said intermediate pressure; (5) said expanded first sfream and said expanded second sfream are directed into a distillation column wherein said streams are separated into a more volatile vapor distillation stream and a relatively less volatile fraction containing a major portion of said heavier hydrocarbon components; (6) a vapor distillation stream is withdrawn from a region of said distillation column below said expanded second sfream and is cooled sufficiently to condense at least a part of it, thereby forming a residual vapor stream and a reflux sfream; (7) said reflux sfream is directed into said distillation column as a top '~ feed thereto; (8) said residual vapor sfream is combined with said more volatile vapor distillation sfream to form a volatile residue gas fraction containing a major portion of said methane and lighter components; and (9) said volatile residue gas fraction is cooled under pressure to condense at least a portion of it and form thereby said condensed stream. 2. In a process for liquefying a natural gas sfream containing methane and heavier hydrocarbon components wherein (a) said natural gas stream is cooled under pressure to condense at least a portion of it and form a condensed sfream; and (b) said condensed stream is expanded to lower pressure to form said liquefied natural gas stream; the improvement wherein (1) said natural gas sfream is treated in one or more cooling steps to partially condense it; (2) said partially condensed natural gas stream is separated to provide thereby a vapor stream and a liquid stream; (3) said vapor stream is divided into at least a first stream and a second stream; (4) said first stream is cooled to condense substantially all of it and thereafter expanded to an intermediate pressure; (5) said second stream is expanded to said intermediate pressure; (6) said liquid stream is expanded to said intermediate pressure; (7) said expanded first stream, said expanded second sfream, and said expanded liquid sfream are directed into a distillation column wherein said streams are separated into a more volatile vapor distillation sfream and a relatively less volatile fraction containing a major portion of said heavier hydrocarbon components; (8) a vapor distillation stream is withdrawn from a region of said distillation column below said expanded second stream and is cooled sufficiently to condense at least a part of it, thereby forming a residual vapor stream and a reflux stream; (9) said reflux stream is directed into said distillation column as a top feed thereto; (10) said residual vapor stream is combined with said more volatile vapor distillation stream to form a volatile residue gas fraction containing a major portion of said methane and lighter components; and (11) said volatile residue gas fraction is cooled under pressure to condense at least a portion of it and form thereby said condensed sfream. 3. In a process for liquefying a natural gas stream containing methane and heavier hydrocarbon components wherein(a) said natural gas stream is cooled under pressure to condense at least a portion of it and form a condensed sfream; and (b) said condensed sfream is expanded to lower pressure to form said liquefied natural gas sfream; the improvement wherein (1) said natural gas stream is treated in one or more cooling steps to partially condense it; (2) said partially condensed natural gas sfream is separated to provide thereby a vapor stream and a liquid stream; (3) said vapor sfream is divided into at least a first sfream and a second stream; (4) said first sfream is cooled to condense substantially all of it and thereafter expanded to an intermediate pressure; (5) said second stream is expanded to said intermediate pressure; (6) said liquid stream is expanded to said intermediate pressure and heated; (7) said expanded first sfream, said expanded second sfream, and said heated expanded liquid sfream are directed into a distillation column wherein said sfreams are separated into a more volatile vapor distillation sfream and a relatively less volatile fraction containing a maj or portion of said heavier hydrocarbon components; (8) a vapor distillation sfream is withdrawn from a region of said distillation column below said expanded second stream and is cooled sufficiently to condense at...
천연 가스 액화 천연 가스의 액화 공정이, 메탄보다 중질인 탄화수소를 주로 함유하는 액체 스트림의 생성과 함께 개시되어 있다. 본 공정에서, 액화시킬 천연 가스 스트림은 부분적으로 냉각시키고, 제1 및 제2 스트림으로 분할한다. 제1 스트림은 추가로 냉각하여 실질적으로 그의 전부를 응축시키고, 중간 압력으로 팽창시키며, 또한 그 후 증류 칼럼으로 제1 중간-칼럼 공급 지점에서 공급한다. 또한, 제2 스트림은 중간압력으로 팽창시키고, 그 후 증류 칼럼으로 제2 하부 중간-칼럼 공급 지점에서 공급한다. 증류 스트림은 제2 스트림의 공급 지점 아래의 칼럼으로부터 인출하고, 냉각하여 그의 적어도 일부를 응축시키고, 환류 스트림을 형성한다. 환류 스트림의 적어도 일부는 증류 칼럼으로 그의 최상부 공급물로써 인도한다. 이 증류 칼럼으로부터의 저부(bottom) 생성물은, 상기 액화 천연 가스의 순도를 감소시키는 메탄보다 중질인 임의의 탄화수소의 대부분을 우세하게 함유한다. 상기 증류 칼럼으로부터의 상기 잔류 가스 스트림은 보다 높은 중간 압력으로 압축하고, 가압하에 냉각하여 이를 응축시키고, 그 후 낮은 압력으로 팽창시켜 액화 천연 가스 스트림을 형성한다. 메탄 및 중질 탄화수소 성분을 함유하는 천연 가스 스트림의 액화 공정으로서, (a) 상기 천연 가스 스트림을 가압 하에 냉각시켜 그의 적어도 일부를 응축시켜 응축된 스트림을 형성하고; 또한 (b) 상기의 응축된 스트림을 보다 낮은 압력으로 팽창시켜 상기 액화 천연 가스 스트림을 형성하는 공정에 있어서, (1) 상기 천연 가스 스트림을 하나 이상의 냉각 단계에서 처리하고; (2) 상기의 냉각된 천연 가스 스트림을 적어도 제1 스트림 및 제2 스트림으로 분할하고; (3) 상기 제1 스트림을 냉각하여 실질적으로 그 전부를 응축시키고 이후 중간 압력으로 팽창시키고; (4) 상기 제2 스트림을 상기 중간 압력으로 팽창시키고; (5) 상기 팽창된 제1 스트림 및 상기 팽창된 제2 스트림을 증류 칼럼 내로 인도하고, 여기서, 상기 스트림들은 보다 휘발성인 증기 증류 스트림 및 상기 중질 탄화수소 성분의 대부분을 함유하는 상대적으로 덜 휘발성인 분획으로 분리되고; (6) 증기 증류 스트림을 상기 팽창된 제2 스트림 아래의 상기 증류 칼럼 영역으로부터 인출하고, 충분히 냉각하여 그의 적어도 일부를 응축시키고, 이에 의해 잔류 증기 스트림 및 환류 스트림을 형성하고; (7) 상기 환류 스트림을 상기 증류 칼럼 내로 최상부 공급물로서 인도하고; (8) 상기 잔류 증기 스트림을 상기의 보다 휘발성인 증기 증류 스트림과 병합하여, 상기 메탄 및 경질 성분의 대부분을 함유하는 휘발성 잔류 가스 분획을 형성하고; 또한 (9) 상기 휘발성 잔류 가스 분획을 가압 하에 냉각시켜 그의 적어도 일부를 응축시키고, 이에 의해 상기의 응축된 스트림을 형성하는 것에 개선사항을 가지는 공정.