Bitumen (also called asphalt) is the residual fraction obtained by fractional distillation of crude oil.
The heaviest derivative which is separated from crude oil in the vacuum distillation unit is the residue of the vacuum distillation which is briefly referred to as “vacuum bottom” or VB. This residue is the main feed for bitumen producing unit.
It is a mixture of organic liquids that are highly viscous, black, sticky, and entirely soluble in carbon disulfide and composed primarily of highly condensed polycyclic aromatic hydrocarbons.
It is the heaviest fraction and the one with the highest boiling point. Since the temperature of bitumen is increased in oxidation process, output of reactor is passed through a cooler and then is sent to storage tanks. By regulating operational variables such as the temperature of reactor, residence time in the reactor, and the ratio of air to feed it will be possible to produce different grades of bitumen for various consumptions such as road and industrial types. Asphalt is primarily used for paving roads. Its main usage is in roads and streets asphalt and insulation. Bitumen is divided into two main groups in usage: paving grade and roofing grade.
Chemically bitumen components are divided into groups of Hydrocarbure, Asphaltine, and Maltin. There is 5-10% max bitumen in Asphaltine which causes the hardness of the bitumen depending on the weather condition and grade of bitumen. Maltin is made of grease and resin.