Bitumen is obtained essentially by distillation of a blend of crudes containing at least one bitumen crude. The others, which are lighter, go to satisfy requirements for different types of fuel and combustibles.
Contrary to a common but mistaken idea, bitumen is not an oil residue that the petroleum industry wants to get rid of at little cost. In reality, to produce bitumen of good quality with constant properties, refiners meticulously select one or more bitumen crudes, following very strict internal approval procedures.
Of the 1300 types of crude oil classified worldwide, only 10 % are suitable for producing bitumen capable of meeting the specifications for use. These types are known as bitumen crudes. In short , bitumen is a blend of hydrocarbons, solid and semi-solid and brown or black in colour.
Having been used as an adhesive, sealant and waterproofing agent for over 8,000 years, its being used in the construction and maintenance of roads, airfields and all areas where asphalt is used; roofing; damp proofing; dam, reservoir and pool linings; soundproofing, pipe coatings, paints, and many others. Asphaltic bitumen is valued for a variety of properties. It is water proof, ductile, adhesive, chemically inert and resistant to atmospheric exposure and the effects of dilute acids and alkalis.
Bitumen is produced from selected crude oils through a process of Fractional Distillation. The crude oil is heated to temperatures of between 300 and 350 degrees Celsius and fed into a distillation column allowing the lightest fractions of the crude to separate, through vaporization, from the heavier fractions, which remain liquid.
The higher boiling point fractions are then drawn-off via a heat exchanger and enter a vacuum distillation column. This process produces a "short residue" that is used to manufacture several grades of bitumen. The pressure and temperature conditions within the vacuum process will determine the hardness of the short residue, and. The short residue may be further modified by 'air blowing' in which air is passed through the residue at temperatures of 250 - 300 degrees Celsius.
Source: http://www.ArticlePros.com/author.php?Ellango
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