Geology Reference
In-Depth Information
Bauxite
Raw materials
preparation
CaO
Digestion
Liquour
heating
Steam
Liquour
flashing
Water
NaOH
Liquour
surge
Sand
preparation
Sand washing
Impurity
removal
Fine residue
separation
Residue
washing
Water
Evaporation
Impurities
Steam
Heating
Cooling
Precipitation
Seed
Residue
disposal
Classification
Water
Washing
Fuel
Calcination
Fig. 8.3 Aluminium production processes (IPPC, 2009)
a quantity which entails about 3.5% of the entire globe's electricity consumption.
The average specific consumption is approximately 52 to 56 GJ/t of aluminium
produced from alumina (15 0:5 kWh/kg Al) (Norgate et al., 2007). This figure
has however declined by about 0.4% per year over the last 25 years but still means
that those in the sector look for sites where electricity is cheapest. Fortunately,
43% of the world primary production is recycled, since the re-melting and refining
of secondary aluminium accounts for only 5% of the energy needed to produce
primary aluminium.
The calcining process of alumina is also a highly demanding energy process.
According to the International Aluminium Institute (IAI, 2008), the global average
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