A process for the
recovery of ethane,
ethylene,
propane, propylene and heavier
hydrocarbon components from a
hydrocarbon gas
stream is disclosed. In recent years, the preferred method of separating a
hydrocarbon gas
stream generally includes supplying at least portions of the gas
stream to a
fractionation tower having at least one
reboiler, and often one or more side reboilers, to supply heat to the column by withdrawing and heating some of the
tower liquids to produce stripping vapors that separate the more volatile components from the desired components. The
reboiler and side reboilers (if any) are typically integrated into the feed stream cooling scheme to provide at least a portion of the
refrigeration needed to condense the desired components for subsequent
fractionation in the
distillation column. In the process disclosed, the
tower reboiling scheme is modified to use one or more tower liquid
distillation streams from a point higher in the column than is used in the conventional reboiling scheme, providing colder stream(s) for the
reboiler(s) that allow more effective cooling of the feed streams and thereby improve the efficiency with which the desired components are recovered. In addition, the tower liquid streams withdrawn from a higher point in the column contain larger quantities of the more volatile components, which when vaporized provide better stripping of undesirable components like
carbon dioxide without reducing the
recovery of the desired components. The heated
distillation stream is returned to a lower point on the
fractionation tower that is separated from the withdrawal point by at least one theoretical stage.