The refining operations consist of three distinct branches: (1) the distillation, (2) the extracting of paraffin and refining, and (3) the chemical treatment. When only a small percentage of the low boiling fractions has to be removed from the crude oil, the process is known as “topping,” and a convenient form of apparatus for the purpose is the tower still. This consists of a vertical cylinder fitted with perforated plates resting at intervals on pipes through which superheated steam travels. The pipes serve the double purpose of conveying the steam to its inlet and of heating the oil to be distilled. The steam, on entering the cylinder, ascends, meeting the crude oil, as it descends from plate to plate in a regulated stream, and carrying with it to the outlet the light fractions which the operation is intended to remove. CRUDE OIL CRACKING DISTILLATION | +-----------------------+----------------+---------------+---------+----------------------------------------------+ | | | | | Crude Naphtha +---------+ Natural Cracked Distillate Tar | | Crude | Lamp Oil | | Steam Distillation | Heavy | Distillate Steam Distillation Mild Cracking | | Naphtha | | | Distillation +------------+-----------+ +----+----+ Acid Treatment +---------+---------+ | | | | | | | | +----------+----+----+-----------+ Gasoline | Bottoms | +---------+ +---------+ +------------+ | | | | +------------+ | | | | Crude | | Test | +------------+ | +----------+ Coke | Naphtha | Steam Sludge Lamp | Naphtha | | Cracked | | Cracked | | | Wax | | Distillate | Distillation | Oil +---------+ | Distillate | | Distillate | | | Tailings | +------------+ | | | +------------+ +------------+ | +----------+