Metallurgy
The extraction of metals from
their ores, heat treatments and
the production of alloys
Production of metals
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Mining
Concentration
Metal extraction
Mining
Five main types of mining:
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Open cast mining
Underground mining
Open pit mining
Dredging
Solution mining
Open cast mining
Underground mining
Open pit mining
Dredging
Solution mining
Ore concentration
Also called ore dressing, the aim is to increase
the amount of metal in each tonne of ore. The
ore is crushed then ground and concentrated,
the following methods may be used:
 Gravity concentration
 Flotation
 Magnetic separation
 Amalgamation
Gravity concentration
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Some ores are heavier than the waste. The
ore is shaken by a jolting box, or similar,
while wet.
Particles will separate into layers depending
on weight, the metal may be removed as a
layer.
Flotation
The fine particles of ore are swirled around
in large tanks with air blown in and flotation
agents added. The particles attach to the
bubbles and float to the surface where the
froth is skimmed off.
Magnetic seperation
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In the seperation of ores that
have magnetic properties, the
ore is ground and passed
over a rotating drum.
The drum has a magnet
inside it which holds the
magnetic ore particles as the
waste falls outside the screen.
The ore held on the drum can
be released or scraped off.
Magnetic seperation
http://www.youtube.com/watch?v=XZjPr8WZtas
Metal extraction
The process of extracting metals from
concentrates:
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Pyrometallurgy – furnace heat is used with a
reducing agent (iron uses coke) and a flux to
produce metal and slag waste.
Hydrometallurgy – leaching dissolves ore in a
solvent and then electrolysis is used to
separate the metal.
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Thermo-electrometallurgy. Aluminium can be
extracted from salt or mineral mixtures by
electrolysis. It uses a lot of electricity making
it an expensive process. Blister copper is
refined by electrolysis.