Light Ends Unit
As shown in Figure 3.2, the Light Ends Unit consists of a sequence of distillation processes to separate the overhead distillate product from the atmospheric distillation column into five streams consisting of methane and ethane (C2 and lighter), to propane (C3), butane (C4), light naphtha, and heavy naphtha. The fraction C2 and lighter is used as fuel gas in the refinery to provide heat or generate steam. Propane and butane are sold as liquefied petroleum gas (LPG) after removing H2S. Light naphtha fraction that consists of C5 and C6 paraffins (pentane and hexane) is sent to the gasoline blending pool as straight-run gasoline, while the heavy naphtha fraction (rich in cycloalkanes, or naphthenes) is sent to a catalytic reforming process to produce gasoline with a high octane number.