Process and apparatus for separating C3 and heavier components from hydrocarbon gases

摘要

In a process for separating a hydrocarbon gas into a fraction (38) containing a predominant portion of the ethane and lighter components and a fraction (31) containing a predominant portion of the C₃ and heavier components, the feed gas is treated in one or more heat exchangers (110, 111, 112), and expansion steps (114, 116) to provide a partly condensed hydrocarbon gas (25) comprising a first residue vapour and a C₃-containing liquid which liquid also contains lighter hydrocarbons; the partly condensed feed gas (25) is directed into a separator (118) wherein the first residue vapour is separated from the C₃-containing liquid; and the C₃-containing liquid (26), at substantially the pressure of separation, is directed into a distillation column (115) wherein said liquid is separated into a second residue (30) containing lighter hydrocarbons and a C₃-containing product. In accordance with the present invention the process is improved by cooling said second residue (30) in a heat exchanger (117) to partially condense it; directing the partially condensed second residue (30) into said separator (118) forming thereby a liquid portion and a vapour portion; intimately contacting at least the first residue vapour of the feed gas (25) with at least the liquid portion of the partly condensed second residue (30) in at least one contacting stage within said separator (118), and thereafter separating the vapours and liquids from said contacting stage; supplying the liquids (26) thereby recovered to the distillation column (115) as a top liquid feed thereto: and directing the vapours (37) thereby recovered to the heat exchanger (117) for heat exchange with the second residue (30) from the fractionation column (115), thereby to partly condense the second residue, and thereafter discharging said residue gases (37).