Environmental Engineering Reference
In-Depth Information
Oil sands are either surface-mined or produced in-situ. Mining works best for deposits
with overburden less than 75 meters thick. Mining requires a hydraulic or electric shovel that
loads the sand into 400-ton trucks, which carry the material to a crusher to be mixed into a
slurry. Using pumps and pipelines, the slurry is “hydro transported” to an extraction facility
to extract bitumen (see figure 3). This process recovers about 90% of the bitumen.[39]
In 2005, mining accounted for about 52% of Alberta's oil sand production (572,000 b/d);
in-situ accounted for about 48% (528,000 b/d), one-third of which was produced using the
Cold Production method in which oil sands are light enough to flow without heat. The in-situ
approach, which was put into commercial production in 1985,[40] is estimated to grow to
926,000 barrels per day by 2012. Currently, the largest production projects are in the Fort
McMurray area operated by Syncrude and Suncor (see table 4 for leading producers of oil
sands).
Extraction Process
The extraction process separates the bitumen from oil sands using warm water (75
degrees Fahrenheit) and chemicals. Extracting the oil from the sand after it is slurried consists
of two main steps. First is the separation of bitumen in a primary separation vessel. Second,
the material is sent to the froth tank for diluted froth treatment to recover the bitumen and
reject the residual water and solids. The bitumen is treated either with a naphtha solvent or a
paraffinic solvent to cause the solids to easily settle. The newer paraffinic treatment results in
a cleaner product.[41] This cleaner bitumen is pipeline quality and more easily blended with
refinery feedstock. After processing, the oil is sold as raw bitumen or upgraded and sold as
SCO.
Figure 4. Continued on next page.
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