In the refinery of crude oil products, there are three main processes, which are: Separation, Conversion, and Treatment.
The basic process of separation is mainly heating crude oil inside a distillation tower to separate components with different properties.
Petroleum is composed of hydrocarbon chains of various lengths. Hydrocarbon chains which are longer in length and contain more carbon atoms have higher boiling points, while smaller chains with less carbon atoms have lower boiling points.
The division into different boiling points and weights is called Fractional Distillation. The crude oil is basically heated in a distillation tower (as seen in the image), which applies the effects of different densities (such as hot and cold air).
The temperature within the tower is lower as the height increases, causing molecules with higher boiling points to remain near the bottom, and those with lower boiling points to separate and rise to various levels along the column. The lightest substances, those with the shortest hydrocarbon chains and fewest carbon atoms, reach their boiling points and rise to the highest, coolest part of the column. As gaseous compounds rise and cool back below their boiling points, they return to liquid form and are collected at various points along the tower.
Gasoline, rises to the top in gaseous form during separation, where it then cools below its boiling point and returns to a liquid state.
Medium weight fractions, which include diesel oil distillates and kerosene, are collected near the center of the tower. The heaviest components, which have the highest boiling points and are thus less affected by the heat inside the column, remain at the bottom of the column. Examples are heavy fuel oils for marine use.
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