The refining process for crude oil
The refining of crude oil for the production of finished goods (LPG, diesel, petrol) is carried out through a process of fractional distillation (a “physical” process), followed by conversion and upgrading operations (processes/transformations of a chemical nature).
Fractional distillation is a two-step process:
- the first step is carried out at atmospheric pressure (primary atmospheric distillation or topping), and, being the most volatile, the first product is LPG. This is followed by increasingly heavy hydrocarbon blends: naphtha (the name given to petrol before further upgrading), kerosene (jet fuel for aircraft) and diesel;
- and a second step in a vacuum (secondary atmospheric distillation or vacuum).
The heaviest components of petroleum products that are not able to evaporate (heavy diesel and residues) are subjected to a conversion process called cracking, with the aim of manufacturing finished products analogous to those produced by atmospheric distillation: i.e. LPG, petrol and diesel.
Theavy diesels are subsequently sent to conversion plants, such as:
- Hydrocraking: processes with high temperature and high pressure hydrogen to obtain diesel;
- FCC: a process of thermal/catalytic cracking to obtain (mainly) petrol;
- solvent extraction: for the production of lubricants.
Different conversion technologies are used at Eni’s refining facilities, in particular: visbreaking, deasphalting, gasification, LC, finfing, and a new technology developed by Eni called EST (see details below).
The products obtained by distillation and conversion are subjected to an upgrading procedure through which they pass through the necessary processes for transformation into finished products: LPG, petrol, jet fuel and diesel. The main processes used for this are:
- desulphurisation with hydrogen, which involves a process for the removal of sulphur to limit the emission of polluting substances;
- optimisation, which is a process aimed at improving the engine performance of petrol.
During the year, at the Sannazzaro de’ Burgondi refinery, a plant for the conversion of residues became fully operational. The plant uses proprietary Eni technology called EST (Eni Slurry Technology) with performance in line with expectations.
The EST technology has the advantage of entirely converting distilled loads and enhancing distillation residues from heavy and ultra-heavy crude oil, as well as non-conventional resources.