Material with a boiling point greater than around 500 °C is considered asphalt. Vacuum distillation separates it from other components in crude oil. The resulting material is typically further treated to extract small but valuable amounts of lubricants and to adjust the properties of the material to suit applications. In a de-asphalting unit, the crude asphalt is treated with either propane or butane in a supercritical phase to extract the lighter molecules, which are then separated. Further processing is possible by “blowing” the product: namely reacting it with oxygen. This step makes the product harder and more viscous.
Asphalt is stored and transported at 150 °C. Sometimes diesel oil or kerosene are mixed in before shipping to retain liquidity. So before delivery, these are separated out of mixture. This mixture is often called “bitumen feedstock” BFS.
The backs of tippers carrying asphalt, as well as some handling equipment, are also commonly sprayed with a releasing agent before filling to aid release. Because of environmental concerns Diesel oil not uses as a release agent.
Naturally occurring crude bitumen impregnated in sedimentary rock is the prime feed stock for petroleum production from “oil sands”, currently under development in Alberta, Canada. Canada has most of the world’s supply of natural bitumen, covering 140,000 square kilometres, giving it second-largest proven oil reserves in the world. The Athabasca oil sands are the largest bitumen deposit in Canada and the only one accessible to surface mining, although recent technological breakthroughs have resulted in deeper deposits becoming producible by in situ methods.
Because of oil price increases after 2003, producing bitumen became highly profitable, but as a result of the decline after 2014 it became uneconomic to build new plants again. By 2014, Canadian crude bitumen production averaged about 2.3 million barrels (370,000 m3) per day and was projected to rise to 4.4 million barrels (700,000 m3) per day by 2020. The total amount of crude bitumen in Alberta that could be extracted is estimated to be about 310 billion barrels (50×109 m3), which at a rate of 4,400,000 barrels per day (700,000 m3/d) would last about 200 years.
Alternatives and bioasphalt:
Although un-competitive economically, asphalt can be made from non-petroleum-based renewable resources. Also can made from waste material by fractional distillation of used motor oil. That may cause premature cracking in colder climates, resulting in roads that need to be repaved more frequently.
Nonpetroleum-based asphalt binders can be made light-colored. Lighter-colored roads absorb less heat from solar radiation, reducing their contribution to the urban heat island effect. Parking lots that use asphalt alternatives are called green parking lots.
Selenizza is a naturally occurring solid hydrocarbon bitumen found in native deposits in Selenice, in Albania. The bitumen is found in the form of veins, filling cracks in a more or less horizontal direction. Bitumen content varies from 83% to 92%, with penetration near to zero and
120 °C softening point. The insoluble matter, consisting mainly of silica ore, ranges from 8% to 17%.
Today mines exploited in open pit quarry. Many underground mines still remain viable. Selenizza produced in granular form, after melting bitumen pieces selected in mine.