Q:
How do you get bitumen out of the oil sands?
A:
The amount of bitumen in Alberta's
oil sands varies from deposit to deposit and even within
deposits. Overall the Athabasca Oil Sands average about
10% bitumen by volume, but in some places the bitumen content
can be as high as 18% or as low as 1%. This means that even
with the richest oil sands more than 80% of the material
mined has to be removed somehow.
The
basic method used to separate bitumen from the water, sand
and clay that make up the rest of the oil sands, is a process
called hot water extraction. This process involves mixing
oil sands with hot water, steam and caustic soda that help
to separate bitumen from the sand. Most of the bitumen rises
to the top of the hot water as froth that can be collected
for further processing. Huge centrifuges, that work much
like cream separators, and inclined plate separators take
the froth and separate it again into water and bitumen.
Other secondary processes further clean and separate the
bitumen, sand and water. When extraction is complete about
98% of the bitumen is removed from the original oil sands
material. The cleaned sand can be used to help reclaim land
at the mine site. Much of the water is recycled or sent
to tailings ponds. The water in these tailings ponds includes
clay and other suspended materials which slowly precipitate
out.
