Technology Unit

: Atmospheric Distillation Column
: Generic ADU
Short Name: Distillation Column
Description: The ADU is a Long Column with many Trays and operates at or above atmospheric pressure (typically 200 kPa). The Trays have Bubble Caps or Holes to allow Vapor to pass through them and are either of the two-pass of four-pass types. Crude Oil enters the ADU in a Tray above the Bottom in the so-called Flash Zone. The Crude Oil vaporizes increasingly as it rises. Liquid,referred to as Atmospheric Residue, is drawn from the Bottom Tray. As the Vapor rises, it passes through the Trays and cools as it comes in contact with the Liquid. Crude fractions settle in trays in the Rectifying Section and are drawn off at five Liquid Side Cuts depending on their average boiling point. The Light Products, which have low boiling point, tend toward the Top and the Heavier Products, with relatively higher boiling points tend toward the Bottom. The Side Cuts are, from Heavy to Light: Heavy Diesel, Medium Diesel, Light Diesel, and Kerosene. The very light Products, e.g., Butane and lighter in addition to Light Naphtha, exit as Vapor at the top of the Column. The atmospheric Overhead is partially condensed in Heat Exchangers. When cooled, the Naphtha condenses and exits as a Liquid while the lighter Products remain as Gases. Uncondensed Vapor flows to the Fuel Gas System, which is used as Fuel for the Furnaces.
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