Basic of refinery

Crude oil is a mix of hydrocarbons, and refining process involves the breaking up of crude oil into a number of products with varying arrangements of atoms of hydrogen and carbon. The refinery process can be bifurcated as under.
· Primary processing
· Secondary processing
· Primary processing
The components of crude oil, which have to be broken up, have different boiling temperatures. Primary processing involves heating of crude oil up to a maximum of about 430º C and subsequent vaporizing of each of the components. The main part of the primary processing unit is the fractionating tower/ crude distillation unit, which is a tall and a cylindrical column through which a mixture of hot vapor and liquid crude is allowed to pass. The lighter compounds/ fractions are collected at the top of the tower and the heavier components are pushed down. The fractionating tower consists of a number of trays filled with special contacting devices and each of the fractions with varying boiling temperatures flow down the respective trays through a cooling process. The compounds, which are normally fractionated from distillation, are Gas & LPG, Naphtha, SKO and HSD. All products except SKO & HSD would require further treatment. The liquid that is still unvaporized flows down as atmospheric residue.
The atmospheric residue, which flows out of the fractionating column, is then heated in the range of 400ºC-600ºC and passed into a High Vacuum Column (HVU). The atmospheric residue is broken up to VGO (Vacuum Gas Oil) and VAC residue (also known as Short residue). VGO is the feed for secondary processing and VAC residue is used for manufacture of FO, LSHS and Bitumen.