What is a refinery?

1. Oil, in the form that it is extracted from deposits, has no practical use whatsoever. For this reason it has to be treated to obtain different compounds that can actually be used for something and this process takes place in refineries.

2. 1.A refinery is an industrial installation in which oil is transformed into products useful for people. The set of operations that are carried out in refineries to make these products are called "refining processes".

Crude oil

1. Petroleum is a complex chemical compound consisting of solid, liquid and gaseous parts.
2. Its composition varies depending on it’s origin but in general it is made up of hydrocarbons (carbon and hydrogen) and small proportions of nitrogen, sulphur, oxygen and metals.

3. It is found naturally in deposits of sedimentary rock and only in places that were once covered by the sea.
4. Petroleum does not form underground lakes; it is always to be found in the pores of porous rock.

Refining processes

1. Separation by distillation. Separation by heating of the various components of crude oil.
2. Conversion. Transformation of intermediary products so that production is tailored to suit current demand and/or their properties are improved.
3. Purification. Elimination or transformation of compounds (water, salt, sulphur, etc.).
4. Blending. Mixing of intermediary products in order to obtain specific end products.

Separation by distillation

- Based on the fact that each of the components of petroleum evaporate at a different temperature. The lightest and most volatile hydrocarbons evaporate first, while the heaviest and least volatile do so last.

- These vapours are later cooled and turned into liquids.
- In order to be able to separate the heaviest fractions the distillation process is carried out in a vacuum (where the pressure is less than that of the atmosphere), thus enabling the distillation temperatures to be reduced.

Conversion

- Cracking: Breaking down the large hydrocarbon molecules into smaller ones in order to increase the amount of light volatile products.

• Cracking by means of heat: viscosity reducers, coking
• Cracking by means of a catalyst: FCC (Fluid catalytic cracking)
• Cracking in the presence of hydrogen: hydrocracking

- Coking: the process used to reduce the surpluses of heavy residual oils of little value, turning them into lighter fuels and at the same time producing coke.

- Alkylation: the opposite process of cracking, in which larger molecules are obtained from smaller ones.

- Reforming and isomerisation: the processes employed to improve the antidetonant quality (octane rating) of gasoline fractions by modifying its molecular structure.

• Continuous catalytic reforming (CCR)
• Semi-regenerative reforming
• Cyclic reforming

Purification and treatment of fractions

- Desalination of crude oil.
- Treatment of sulphur content by means of extraction techniques or sweetening (e.g. MEROX technology), hydrodesulphurisation (HDS), washing with amines, etc.
- Hydrodesulphurisation o hydrotreatment (HDS/HDT) of fractions to eliminate sulphur compounds and/or any that are unsaturated, unstable, nitrogenous, etc.
- Amine treatment of gases and light fractions to eliminate hydrogen sulphide (H2S) and other sulphur and non-sulphur compounds.
- Sulphur recuperation from gas streams, principally by means of the Claus process.
- Treatment of sour water stripping with steam.

Blending

- Mixing intermediary products for the purpose of obtaining specific end products.

Products