Crude Fractionation

Crude oil is pumped through a preheating train, which heats the feed by cross exchange with hot distillate products kerosene, diesel, and atmospheric residue. A desalter to remove salts via the addition of heat and contact with fresh water can be added to prevent the formation of hydrochloric acid.

The heated feed flows to the flash drum where vapours are evolved and separated. Alternatively a prefractionator can be utilized upstream to remove light ends, reducing vapour traffic in the main crude tower. The crude is further preheated via heat exchange with hot residue prior to flowing to the crude feed heater, which vapouizes approximately 75 wt%. The crude and separated vapours are introduced as individual feeds to the fractionator, a refluxed distillation column with side strippers to facilitate the separation of distillate products via contact between counter flowing liquids and vapours. Superheated steam generated from heat exchange with hot residue product is introduced to the tower and strippers, as a stripping agent to remove light end components from the liquid product streams.

Naphtha exits the top of the tower, is condensed with a portion returned as reflux and the remainder blended with light naphtha to meet specification. Distillate products are drawn from intermediate points in the tower and pumped from the bottom of each stripper, to preheat exchangers in the preheating train, where they are cooled and continue downstream for storage. Residue product is pumped from the tower bottoms and cooled through a series of heat exchangers prior to storage and export.