Cold separation of gas mixtures

摘要

1,068,981. Cold separation of gas mixtures. CONCH INTERNATIONAL METHANE Ltd. Feb. 23, 1966 [March 19, 1965], No. 7851/66. Heading F4P. Separation of a compressed hydrocarbon gas mixture, e.g. refinery tail gas comprising methane and heavier saturated and unsaturated hydrocarbons into liquid and gaseous fractions is effected by cooling in an indirect heat exchanger (24) traversed by liquefied natural gas means so as to partly condense the feed mixture, withdrawing from a separator (34) uncondensed feed gas through a line (38), compressing at (40) to a pressure above that of the feed gas, cooling in exchanger (24) and in an exchanger (46) also cooled by L.N.G. withdrawing -the condensed C 2 and C 3 hydrocarbons from a separator. (4) through a line (54) and withdrawing uncondensed methane contaminated with hydrogen, nitrogen and carbon monoxide through a line (59). Crude condensate from separator (34) is expanded at (36) into a de-methanizer column (20) then fed through a line (67) to a de-ethanizer column (4) from the base of which crude liquid propane is withdrawn through a line (88) and passed into a propylene splitter column (92). Product liquid propane is discharged from column (92) through a line (110) and gaseous propylene through a line (96) and a condenser (102) to be discharged as product liquid propylene through a line (106). The condensed C 2 , C 3 hydrocarbons in line (54) are also passed to de-methanizer column (20) and from thence to de-ethanizer column (4). Gaseous ethylene and ethane withdrawn from column (4) are passed through a line (68) to an ethylene splitter (16) from which gaseous ethylene is withdrawn through a line (70) expanded at (72) condensed, at (74) and discharged as product liquid ethylene through a line (78). Gaseous ethane is also withdrawn from splitter (16) through a line (80) and after being condensed at (82) is discharged by a pump (84) as product through a line (86). The coolant L.N.G. which is admitted through a line (112) and is pressurized by a pump (114) and after being warmed in exchangers (24, 26) serves to cool condensers (82, 102) and reflux coils (126, 128) in columns (4, 16). To the so-vaporized natural gas in line 144 is added a gaseous stream of methane, hydrogen, carbon monoxide and nitrogen withdrawn from the head of de-methanizer (20) through a line (66) and a compressor (65) and a consumer line (146).