Bitumen

Figure 1. Bitumen is a thick, black crude oil.

Bitumen is an extremely heavy, highly viscous form of crude oil composed of complex hydrocarbons. In an oil reservoir, bitumen is a thick, viscous fluid and must be extracted from the ground. Extracting and upgrading bitumen require significant amounts of heat and energy to produce lighter petroleum products. Although bitumen is hard to extract from the ground, it can bubble naturally to the surface of the Earth in petroleum seeps. These seeps are places where petroleum or natural gas naturally leaks to the Earth's surface instead of remaining trapped deep underground. In these seeps, bitumen or crude oil can accumulate in naturals pools at the surface. Additionally, bitumen is the main fossil fuel component of oil sands. Bitumen contains asphaltines, which contribute to its strength and adhesive properties, making it useful as the binder in asphalt used for paving roads.

Production

In addition to being found naturally in seeps and the oil sands, bitumen can remain by removing lighter fractions from crude oil during the refining process. Some of the lighter fractions removed during refining include liquefied petroleum gas (LPG), gasoline, and diesel fuel.

Once crude oil has been extracted from the ground, refinery bitumen can be obtained during the refining process. The crude oil is pumped from the storage tanks and through a system that increases the temperature of the crude oil to 200°C. The oil then moves to a furnace, where it is heated even higher to approximately 300°C and partially vaporized before entering a distillation column. Here, the separation of the different components of the crude oil occurs. As lighter components rise toward the top, the heavier fractions remain near the bottom of the column. This process is known as fractional distillation. Finally, the bitumen is obtained by further distilling the residue in a vacuum distillation column. This type of bitumen is known as straight-run bitumen. The grade of the bitumen depends on how much volatile material remains after distillation, with more volatile components producing a softer, less viscous product.

Use

Most refined bitumen is used in the construction industry. It is primarily used in paving and roofing applications. Approximately 85% of bitumen is used as a binder in asphalt for roads, runways, parking lots, and footpaths. Gravel and crushed rock are mixed with bitumen, which acts as a binder to hold the aggregate together before the mixture is applied to roadways. Approximately 10% of bitumen is used in roofing materials because of its waterproofing properties. The remaining 5% is used in a variety of industrial applications, including sealing, insulation applications in building materials such as carpet tile backing and paint.

In addition to these main uses, bitumen also has many minor uses. Other applications include soundproofing, explosives, mildew protection, binders for briquettes, mirror backing, shoe soles, fence post coatings, and soil stabilization.

For Further Reading

• Bitumen upgrading
• Crude oil
• Fossil fuel formation
• Fractional distillation
• Or explore a random page