An oil refinery is a facility where crude oil is processed into various chemical products and by-products. These products are used for a multitude of industrial and commercial applications. The most common chemicals produced by refineries are fuels and lubricants such as gasoline, kerosene, and motor oil. An oil refinery produces a multitude of other chemicals, including the ingredients for plastics and other useful materials. Some by-products of the oil refining process also have industrial applications, such as petroleum coke, which is used in steel manufacture.
Oil refineries are usually large industrial complexes filled with the complex network of machinery necessary for chemical processing. Most are connected by pipelines to oil production facilities; if this is not possible, trains or other transport methods must be used to deliver crude oil to the refinery. They are often located near large bodies of water, because water is used as a coolant and in some chemical processes. The average oil refinery has numerous internal pipelines for moving both processed and unprocessed chemicals throughout the site and large tanks for storing those chemicals. Most refineries are located far from residential areas because of noise, emissions, and safety concerns.
Once crude oil enters the oil refinery, it is refined by a process called fractional distillation. This process separates the oil into various forms, or fractions, that are distinguished by their molecular structure. All of these petroleum distillates, or petrochemicals, are composed of complex molecules called hydrocarbons. Some of these petrochemicals are useful on their own, while others must be processed further at the oil refinery or another site. These further chemical processes vary depending on the kind of distillate and the desired end product.
Gasoline, also known as petrol, is the primary product of petroleum processing, along with other fuels such as diesel, kerosene, and liquefied petroleum (LP) gas. Petrochemicals are also used to create numerous products, including waxes, solvents, and pesticides. Asphalt and tar from petroleum are used in the construction of roads and buildings. Polymers produced from petrochemicals form the basis of many plastics. Useful by-products of the oil refinery include petroleum coke, a necessary ingredient for making steel and aluminum, and sulfuric acid, which can be reused in the oil refining process.
An oil refinery is a costly and complicated operation. High demand for product requires many refineries to operate continually, allowing few opportunities for maintenance or improvements. Stringent environmental and safety regulations control the location, activity, and emissions of refineries. Increased awareness of environmental concerns has focused scrutiny on these facilities, which can generate pollutants and carcinogens and reduce air quality. Nevertheless, many of the products created by oil refineries are essential for modern society.