Atmospheric Distillation Tower - continued

The figure provided here illustrates a schematic diagram for an atmospheric distillation tower.

At the refinery, the desalted crude feedstock is first preheated by a direct-fired crude charge heater to approximately 650-700 deg F (343–370 deg C). Heating crude oil above these temperatures is likely to cause undesirable thermal cracking. After heating, the crude is fed into a vertical distillation column, at a location just above the bottom.

The pressure at the location, where the incoming crude oil is fed, is slightly above atmospheric pressure. As the feed stream enters, all but the heaviest fractions flash into vapor. As the hot vapor rises in the tower, its temperature is reduced.

Heavy fuel oil or asphalt residue collects at the bottom.

At successively higher points on the tower, various major products including lubricating oil, heating oil, kerosene, gasoline, and uncondensed gases are drawn off.