Description
Bitumen
Asphalt is a sticky, black and highly viscous liquid or semi-solid
form of petroleum. It may be
found in natural deposits or may be a refined product; it is a
substance classed as a pitch. Until
the *0th century, the term asphaltum was also used. The word is
derived from the Greek
\'asphaltos\' which in turn was borrowed from an Eastern word.
The primary use (*0%) of asphalt/bitumen is in road construction,
where it is used as the glue or
binder mixed with aggregate particles to create asphalt concrete.
Its other main uses are
for bituminous waterproofing products, including production of
roofing felt and for sealing flat
roofs.
The terms asphalt and bitumen are often used interchangeably to
mean both natural and
manufactured forms of the substance. In American English, asphalt
(or asphalt cement) is the
carefully refined residue from the distillation process of selected
crude oils. Outside the United
States, the product is often called bitumen. Geological terminology
often prefers the
term bitumen. Common usage often refers to various forms of
asphalt/bitumen as "tar", such as
at the La Brea Tar Pits. Another term for asphalt/bitumen, now
rather archaic, is "pitch".
Naturally occurring asphalt/bitumen is sometimes specified by the
term "crude bitumen". Its
viscosity is similar to that of cold molasses while the material
obtained from the fractional
distillation of crude oil boiling at **5 °C (**7 °F) is sometimes
referred to as "refined bitumen".
5.1 Bitumen-based fuel
Fuel specifically developed for industrial use. The most known
bitumen-based fuel
is Orimulsion, an emulsion of natural bitumen from Orinoco Belt and
fresh water, which was
developed by Intevep.
Raw bitumen has an extremely high viscosity, between 8 to *0 API
degrees, at ambient
temperatures, rendering it unusable for use in electrical power
stations. Bitumen can be modified
by mixing it with fresh water and a small amount of phenol-based
surfactant. The resulting
mixture has properties similar to conventional fuel oil.
A newer version of bitumen-based fuel has replaced the original
version with an alcoholbased
surfactant, making it easier to transport the fuel and eliminating
the health concerns
associated with the phenol group of surfactants.
Bitumen-based fuel is currently used as a commercial boiler fuel in
power plants
in Canada, Japan, Lithuania, and China). Commonly available air
pollutant control technology
can limit emissions from Orimulsion to levels considered Best
Available Control Technology, as
defined by the United States Environmental Protection Agency.
