Before discussing petroleum refining, it is important to understand petroleum itself. Briefly defined, it is a complex mixture of organic liquids called as crude oil, and natural gas. The mixture was formed millions years ago, deep below the earth. The varieties of crude oil differ from oilfield to oilfield in composition and color, from a low viscosity liquid with pale yellow color, to consistencies of heavy black ‘treacle’.
From the earth and water, natural gas and crude oil are extracted, and then transported to a refinery by using pipes, ships, or both. Raw crude oil and natural gas are rarely used for energy purposes, so they are broken down into multitudes of different products, such as: waxes, fuels, petrochemicals, and asphalt.
The petroleum refining is coordinated, well organized manufacturing process. A refinery is designed for changing physical and chemical properties of crude oil, that it may be converted into more usable products.
Because the crude oil is mined from a well, it contains a mixture of compounds of hydrocarbon and rather small quantities of other materials such as nitrogen, salt, oxygen, sulphur and water. These non-hydrocarbon substances are removed before being converted into different oil byproducts.
Petroleum refining begins with the separation of crude oil into different fractions through a process called ‘distillation.’ The fractions are treated further to convert them into a mixture of marketable products through a large list of methods and processes: reforming, polymerization, alkylation, cracking and isomerisation. These new compound mixtures are separated afterwards, by using solvent extraction and fractionation. Through the following later stages, sulphur and other impurities are removed using hydro-treating and dehydration.
The processes of refinery have developed as a response to the changing demands of the global market. The main task of refineries became petrol/gasoline production, with the advent of the internal combustion engine. However, the available quantity from distillation alone was insufficient for consumer demands. As a result, refineries explored new methods and procedures to increase both quality and quantity in the production of petrol. The larger process of petroleum refining was then divided into breaking heavy, large hydrocarbon molecules down, and subsequently rebuilding or reshaping the molecules of hydrocarbon.
Today, refineries continue to explore new options for petroleum production, both for greater efficiency and complying with increasing demands from environmental and government codes and regulations.