Crude Oils & Refined Products
Crude oil
The basic characteristics of crude oil are measured in terms of density and of sulphur content. The density is classified by the American Petroleum Institute in terms of API degrees (°API). The higher the °API, the lighter the crude. Light crude exceeds 35 °API, while heavy oils are those with a density of less than 25 °API. Crude oil between 25 and 35 °API is generally called medium crude. As far as the sulphur content is concerned, crude is commonly defined as sweet if it has a sulphur content of less than 1% in weight and defined as sour in the opposite case. Light crude with a low sulphur content is more expensive than heavy crude with a higher sulphur content because it requires less treatment and has a better yield of more valuable products, such as gasoline, diesel and jet fuel.
Fuels
An initial distinction can be made within the fuels of petroleum origin, it is that between carburetants and combustibles.
This distinction generally implies the mechanism by which the mixing with air in the phase that precedes combustion is done. According to this distinction LPG, gasoline and aviation kerosene, but not diesel, are carburetants. In everyday language, the definition of carburetants is still wider, even if technically less strict, energy products designated for internal combustion engines are defined as "automotive fuels" or carburetants, this therefore includes diesel. The exception is residual fuel oil, which feeds large marine and fixed diesel engines, which is combustible by definition.
LPG
LPG, or liquefied petroleum gas, is a mixture of very light hydrocarbons with gaseous qualities at atmospheric pressure and which liquefies at environmental temperature and not very high pressure. It is sold on the market as propane, butane or as a blend of them. Like natural gas, LPG is an energy source with a low environmental impact and is mainly used in the residential and transport sectors.
Gasoline
Gasoline is defined as a mix of light hydrocarbons, with molecules of 4 to 12 carbon atoms, liquid at ambient temperature and pressure conditions, suitable to be used for internal combustion engines with spark ignition.
Kerosene
Kerosene is a product largely obtained from the primary distillation of crude oil. The main use for kerosene is in aviation turbine engines (jet fuel), while its use for heating purposes is less relevant.
Diesel (Gasoil)
Gasoil (also defined middle distillate) is obtained both from a specific portion of crude oils and from the conversion of heavier fractions during the refining process. It is mainly used in thermal systems for heating purposes. Diesel fuel is very similar to gasoil but is characterized by higher quality because of a stricter set of specifications, and is used for the supply of internal combustion engines with spontaneous ignition
Fuel Oil
Fuel oil is a mix of heavy hydrocarbons which is obtained by diluting a high viscosity residue with lighter oil products, such as gasoil. The main uses of fuel oil are for the production of steam for industrial uses or for the generation of electric energy and for large diesel ship engines.
Bio-diesel
Diesel fuel which contains components derived from renewable raw materials, such as vegetable oils and animal fat.
Last update 20/05/08