EP0026229A1 — Cryogenic recovery of liquids from refinery off-gases

USPTO Abstract

A fraction of vapor containing hydrogen and at least one hydrocarbon chosen from the group of C1 to C4 hydrocarbons is separated from a residual refinery feed gas to give a fraction of liquid product. This residual refinery gas (1) is supplied and compressed by a compressor / holder (21) having compression (20) and expansion (24) means mounted and actuated by the same axis (25) and then cooled and partially condensed to form a two-phase fluid (4) in a heat exchanger (22) followed by separation of the vapor (5) and the liquid (9) from the phases of the fluid product in a separator (23) or a column unit stabilized separation / fractionation (30). The separate vapor phase (5) is transmitted to the compressor / holder unit (21) in which the vapor is expanded and partially condensed, thereby actuating the compressor (20). The fraction of partially condensed expanded vapor (17) from the holder (24) and, optionally, the fraction of liquid phase product (9, 10) from the separator (23) are transmitted in separate currents to the heat exchanger (22 ) for separate thermal contact with the compressed feed gas (2) in which the partially condensed expanded vapor fraction (7) is completely vaporized and the feed gases are cooled. The fully vaporized fraction and the liquid fraction (13) are recovered in different streams.