an Australian petroleum resource
In Australia, oil shale deposits exist in N.S.W and Qld. An oil shale deposit was worked for 40 years at Joadja, near Mittagong. It closed due to imports of 'cheap' kerosene. Another deposit, at Glen Davis, west of Sydney in N.S.W., was worked during WW2. It closed in 1952.
The latest shale oil refinery has
been built near Gladstone, Queensland. It treats shale from the
Stuart deposit. The deposit is about 18 km long, 3 km wide and
400 m deep. The material is extracted using open cut methods. In
the first stage high grade shale (13% oil) is mined.
The shale is crushed to increase the surface area. The crushed
particles are about 6 mm in diameter.
Crushing does not release any oil. Although we talk about oil
shale, it's not easy to get oil from this rock. If you throw it
onto an open fire, it will burn with a smell of kerosene leaving
much ash.
"Warning...I have seen it explode on an open fire.
In the dryer, the moisture content
of the shale is reduced. When the shale is mined up to 25% of the
weight is moisture. The drying uses excess heat from the
processor.
In a rotating cylindrical processor, thermal decomposition of the
kerogen occurs.
Hold on. What's
kerogen?
Oil shale is a sedimentary
rock containing solid hydrocarbon (kerogen). The kerogen was
formed in large fresh or salt water lakes from deposits of
spores, pollen and algae. It is just like a mineral in the rock.
What happens in
the processor?
* Crushed shale is completely
dried and heated to 250oC.
* The heated shale mixes with hot, spent shale. The temperature
rises to 500oC. The kerogen decomposes.
* Carbon remaining in the shale is burned for heat energy.
What is formed
when the kerogen decomposes?
Hydrocarbon gases, petroleum
coke, nitrogen compounds, sulfur compounds.
Why are nitrogen
and sulfur compounds formed?
Kerogen is the result of
microscopic living material. All living material contains
proteins and nucleic acids.
Proteins contain carbon, hydrogen, oxygen, nitrogen and sulfur.
Proteins are built up from amino acids.
Nucleic acids contain carbon, hydrogen, oxygen, nitrogen and
phosphorus.
The hydrocarbon gases are cooled. The liquids produced are
fractionated into only two fractions.
The naphtha (C4 to C10) fraction is purified.
What are two
possible byproducts?
Sulfuric acid from the sulfur
compounds. Ammonia from the nitrogen compounds.
The naphtha and light oil fractions are stored.
How much does it cost to produce these hydrocarbons? About $18 a barrel while production is still low.
What happens to
the liquid hydrocarbons?
The naphtha is sold to local
oil refineries. The light oil is exported.
