Acid Plant

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Acid Plant
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Sulphur Dioxide (SO2)
2SO2
If you remember the Roasting Process we discussed
how the sulphur is separated from the zinc
concentrate and liberated as sulphur dioxide
gas.
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For environmental reasons, we cannot allow the
sulphur dioxide to be emitted into the
atmosphere. Also, we can use the sulphur
dioxide gas to make a valuable commodity -
sulphuric acid.
The waste sulphur dioxide gas from the Roasting
process is transferred to the Acid Plant for
conversion into sulphuric acid.
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The sulphur dioxide gas is initially cleaned to
extract any fine calcine dust and then
cooled. It is then dried by passing it through
a concentrated, sulphuric acid mist to reduce the
humidity or moisture content.
Storage Tanks
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Sulphuric acid
Air (02) for conversion of SO2 to SO3
Dry S02 gas
Sulphuric acid mist
Pure S02 gas at 38oC but with a humidity of 7- 8
Calcine dust back to Roaster
2. Gas Drying
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The use of a catalyst, vanadium pentoxide (V2O5),
is the accelerate the reaction between sulphur
dioxide gas and oxygen. This allows the sulphur
dioxide (SO2) gas to be easily converted into
sulphur trioxide (SO3) gas.
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4. Absorption
The SO3 gas reacts with the H2O to form H2SO4
(sulphuric acid).
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The sulphuric acid is pumped into large storage
tanks.
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Conclusion
This concludes our journey through the zinc
refining process. As you can probably appreciate
by now, it is a complex and highly scientific
process to refine zinc metal from concentrated
zinc ore. You have just witnessed how we can
produce approximately 200,000 tonnes of zinc
metal and 370,000tonnes of sulphuric acid per
year.