What are Tar sands exactly?
Tar sands, also referred to as oil sands or bituminous sands, are a combination of clay, sand, water, and bitumen(a heavy, viscous form of crude oil).
Bitumen is neither oil nor tar, but a semisolid, degraded form of oil that does not flow at normal temperatures and pressures, making it difficult and expensive to extract.
The bitumen in tar sands cannot be pumped from the ground in its natural state; instead tar sand deposits are mined, usually using strip mining or open pit techniques or produced in-situ by underground heating or other tertiary recovery processes. As open pit mining has now become cost-effective we'll focus on this method exclusively.
Tar sands deposits near the surface are recovered by open pit mining techniques. New methods introduced in the 1990s considerably improved the efficiency of tar sands mining, thus reducing the cost. These systems use large hydraulic and electrically powered shovels to dig up tar sands and load them into enormous trucks that can carry up to 320 tons of tar sands per load.
Tar sands are mined and processed to generate oil similar to oil pumped from conventional oil wells, but extracting oil from tar sands is more complex than conventional oil recovery. Oil sands recovery processes include extraction and separation systems to separate the bitumen from the clay, sand, and water that make up the tar sands.
Bitumen also requires additional upgrading before it can be refined. Because it is so viscous(thick), it also requires dilution with lighter hydrocarbons to make it transportable by pipelines.
After mining, the tar sands are transported to an extraction plant, where a hot water process separates the bitumen from sand, water, and minerals. The separation takes place in separation cells. Hot water is added to the sand, and the resulting slurry is piped to the extraction plant where it is agitated.
The combination of hot water and agitation releases bitumen from the oil sand, and causes tiny air bubbles to attach to the bitumen droplets, that float to the top of the separation vessel, where the bitumen can be skimmed off.
Further processing removes residual water and solids. The bitumen is then transported and eventually upgraded into synthetic crude oil. About two tons of tar sands are required to produce one barrel of oil. Roughly 75% of the bitumen can be recovered from sand. After oil extraction, the spent sand and other materials are then returned to the mine, which is eventually reclaimed.
Where are tar sands found?
Oil sands are found primarily in the Athabasca region of northern Alberta, Canada. Which fulfills one important wish of western coutries: reducing energy dependence from instable countries. However the environmental impact of extracting oil from sand is considerable.
Environmental impact.
Both mining and processing of tar sands involve a variety of environmental impacts, such as global warming and greenhouse gas emissions, disturbance of mined land; impacts on wildlife and air and water quality. A special concern is the large amount of water required for tar sands processing; currently, tar sands extraction and processing require several barrels of water for each barrel of oil produced, though some of the water can be recycled.
Previous Energy Focus