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Oil refinery

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View of Shell Oil Refinery in Martinez, California.
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View of Shell Oil Refinery in Martinez, California.

An oil refinery is an industrial process plant where crude oil is processed and refined into useful petroleum products, such as gasoline and diesel fuel.

Contents

Operation

Crude oil is separated into fractions by fractional distillation. The fractioning column is cooler at the top than at the bottom so the vapours can condense more easily while the moving up the column. The heavier fractions that emerge from the bottom of the fractionating column are often broken up (cracked) to make more useful products.
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Crude oil is separated into fractions by fractional distillation. The fractioning column is cooler at the top than at the bottom so the vapours can condense more easily while the moving up the column. The heavier fractions that emerge from the bottom of the fractionating column are often broken up (cracked) to make more useful products.

Raw oil or unprocessed ("crude") oil is not very useful in the form it comes in out of the ground. Although "light, sweet" (low viscosity, low sulfur) oil has been used directly as a burner fuel for steam vessel propulsion, the lighter elements form explosive vapors in the fuel tanks and so it is quite dangerous, especially so in warships. For this and many other uses, the oil needs to be separated into parts and refined before use in a solid material such as plastics and foams, or as petroleum fossil fuels as in the case of ship, automobile and aircraft engines. These different hydrocarbons have different boiling points, which means they can be separated by distillation. Since the lighter liquid elements are in great demand for use in internal combustion engines, a modern refinery will convert heavy liquid and lighter gaseous elements into these higher value products using complex and energy intensive processes.

Oil can be used in so many various ways because it contains hydrocarbons of varying molecular masses and lengths such as paraffins, aromatics, naphthenes (or cycloalkanes), alkenes, dienes, and alkynes. Hydrocarbons are molecules of varying length and complexity made of hydrogen and carbon. Their various structures give them their differing properties and thereby uses. The trick in the oil refinement process is separating and purifying these.

Once separated and any contaminants and impurities have been removed, the oil can be either sold without any further processing, or smaller molecules such as isobutane and propylene or butylenes can be recombined to meet specific octane requirements by processes such as alkylation or less commonly, dimerization. Octane can also be improved by catalytic reforming, which strips hydrogen out of hydrocarbons to produce aromatics, which have much higher octane ratings. Intermediate products such as gasoils can even be reprocessed to break a heavy, long-chained oil into a lighter short-chained one, by various forms of cracking such as Fluid Catalytic Cracking, Thermal Cracking, and Hydrocracking. The final step in gasoline production is the blending of fuels with different octane ratings, vapor pressures, and other properties to meet product specifications.

Products of oil refinery

Safety and environmental concerns

MiRO refinery at Karlsruhe
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MiRO refinery at Karlsruhe

Oil refineries are typically large sprawling industrial complexes with extensive piping running throughout. The refining process releases numerous different chemicals into the atmosphere; consequently, there are substantial air pollution emissions[AP 42, Compilation of Air Pollutant Emission Factors] and a notable odor normally accompanies the presence of a refinery. Aside from air pollution impacts there are also wastewater concerns, upset risks of fire and explosion, and both occupational noise and environmental noise health effects.

The public has demanded that many governments place restrictions on contaminants that refineries release, and most refineries have installed the equipment needed to comply with the requirements of the pertinent environmental protection regulatory agencies. In the United States, there is strong pressure to prevent the development of new refineries, and no major refinery has been built in the country since Marathon's Garyville facility in 1976. However, many existing refineries have been expanded during that time. It is likely that more stringent conditions will be placed on refineries in the future worldwide, leading to a change in the net energy balance of production against petroleum and in favor of ethanol fuel. These environmental restrictions and pressure to prevent construction of new refineries have also contributed to rising fuel prices in the Unites States.

Environmental and safety concerns mean that oil refineries are sometimes located some distance away from major urban areas. Nevertheless, there are many instances where refinery operations are close to populated areas and pose health risks such as in Tenerife, Spain [Smoke, oil spills and now radiation - whatever next?] www.atan.org , which is sited in a densely-populated city center and next to the only two major evacuation routes in and out of the city. In California's Contra Costa County and Solano County, a shoreline necklace of refineries and associated chemical plants are adjacent to urban areas in Richmond, Martinez, California, Pacheco, Concord, Pittsburg, Vallejo and Benicia, with occasional accidental events that require "shelter in place" orders to the adjacent populations.

Common process units found in a refinery

Specialized end product units

These will blend various feedstocks, mix appropriate additives, provide short term storage, and prepare for bulk loading to trucks, barges, product ships, and railcars.

Co-plant siting

Frequently a chemical plant will be sited adjacent to a refinery, utilizing intermediate products as feedstocks for the production of specialized materials such as plastics or agrichemicals.

History

The world's first oil refinery opened at Ploieşti, Romania in 1856 [WORLD EVENTS: 1844-1856] www.pbs.org. Several other refineries were built at that location with investment from United States companies before being taken over by Nazi Germany during World War II. Most of these refineries were bombarded by the US Air Force in Operation Tidal Wave, August 1, 1943. Since, they have been rebuilt, and currently pose somewhat of an environmental concern.

Another early example is Oljeön, now preserved as a museum at the UNESCO world heritage site Engelsberg. It started operation in 1875 and is part of the Ecomuseum Bergslagen.

The largest oil refinery in the world is in Ras Tanura, Saudi Arabia, owned by Saudi Aramco. The city was originally built as a sea port, but actually developed because of the huge refinery area. For most of the 20th century, the largest refinery of the world was that of Abadan in Iran.

Early US refineries processed crude oil to recover the kerosene. Other products (like gasoline) were considered wastes and were often dumped directly into the nearest river. The invention of the automobile shifted the demand to gasoline and diesel, which remain the primary refined products today. Refineries pre-dating the EPA were very toxic to the environment. Strict legislation has mandated that refineries meet modern air and water cleanliness standards. In fact, obtaining a licence to build even a modern refinery with minimal impact on the environment (other than CO2 emmissions) is so difficult and costly that no new refineries have been built in the United States since 1976. As a result, the US is becoming more and more dependent on the imports of finished gasoline, as opposed to incremental crude oil.

See also

A refinery at night. The gas flare is in the center of the picture.
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A refinery at night. The gas flare is in the center of the picture.

References

External links

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