Atmospheric distillation of crude oil
Refining of crude oils essentially consists of primary separation processes and secondary conversion processes. The petroleum refining process is the separation of the different hydrocarbons present in crude oil into useful fractions and the conversion of some of the hydrocarbons into products having higher quality performance.
Atmospheric and vacuum distillation of crude oils are the main primary separation processes producing various straight run products, e.g., gasoline to lube oils/vacuum gas oils. Distillation of crude oil is typically performed first under atmospheric pressure and then under a vacuum. Low boiling fractions usually vaporize below 400°C at atmospheric pressure without cracking the hydrocarbon compounds. Therefore, all the low boiling fractions of crude oil are separated by atmospheric distillation. A crude distillation unit (CDU) consists of the pre-flash distillation column. The petroleum products obtained from the distillation process are light, medium, and heavy naphtha, kerosene, diesel, and oil residue.