What is Bitumen?
Petroleum Bitumen is a hydrocarbon product produced by removing the lighter fractions (such as liquid petroleum gas, petrol and diesel) from crude oil during the refining process. It’s an engineering material and is produced to meet a variety of specifications based upon physical properties. Bitumen is the residual product from the distillation of crude oil in petroleum refining. The basic product is sometimes referred to as ‘straight run’ bitumen and is characterized by CAS# 8052-42-4 or 64741-56-6 which also includes residues obtained by further separation in a deasphalting process.
Bitumen is a black or dark-colored (solid, semi-solid, viscous), amorphous, cementitious material that can be found in different forms, such us rock asphalt, natural bitumen, tar and bitumen derived from oil, which is referred to as petroleum bitumen.
The Uses of Bitumen
The vast majority of bitumen is used by the construction industry, as a constituent of products used in paving and roofing. Excellent waterproofing characteristics and thermoplastic behavior make it ideal for a wide range of applications. At elevated temperatures (typically between 100 and 200C) it acts like a viscous liquid, and can be mixed with other components and manipulated and formed as required. Once cooled, it is an inert solid that is durable and hydrophobic (repels water).
- 85% Paving
- 10% Roofing
- 5% Other Purposes
About 85% of all the bitumen produced in the world is used in asphalt for the construction of roads and other paved areas. Typically, asphalt will contain approximately 5% by mass of bitumen, with the remaining 95% consisting of a mixture of mineral aggregates and much finer materials such as limestone filler. A further 10% of global bitumen production is used in roofing applications, and the remaining 5% is used mainly for sealing and insulating purposes in a variety of building materials, such as pipe coatings, carpet backing, joint sealants and paint.
How is Bitumen Procuced?
The crude oil is pumped from storage tanks, where it is kept at about 60°C, through a heat exchanger system where its temperature is increased to typically 200°C by exchanging heat gained from the cooling of newly produced products in the refining process. The crude is then further heated in a furnace to typically 300° C where it is partly vaporized into an Atmospheric Distillation Column. Here the physical separation of the components occurs. The lighter components rise to the top and the heaviest components (the atmospheric residue) fall to the bottom of the column and pass through a second heat exchanger prior to treatment in a vacuum distillation column. Finally, Bitumen is obtained by vacuum distillation or vacuum flashing of atmospheric residue from the vacuum distillation column. This is “straight run bitumen”. This process is called bitumen production by straight run vacuum distillation.
An alternative method of bitumen production is by precipitation from residual fractions by propane or butane-solvent deasphalting. The bitumen thus obtained has properties which derive from the type of crude oil processed and from the mode of operation in the vacuum unit or in the solvent deasphalting unit.