The next
step is the actual process of extraction from the clean and dry mineral
particles.
The
enriched sulfide ore is first converted into the oxide by roasting it in
air.
–2ZnS (s) + O2 (g) à ZnO(s) + SO2 (g)
Then what
follows is very similar to the processes carried out in the extraction
of iron from hematite.
The oxide is heated
in a blast furnace with coke.
Carbon monoxide
reduces zinc oxide to zinc.
–2ZnO (s) + CO (g) à Zn (g) + CO2 (g)
–Notice that zinc vapor
is produced instead of molten zinc because the temperature (of over
1000°C) in the
furnace is higher than the boiling point (992°C) of zinc.