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SMELTING:
The Imperial Smelting furnace operated at Avonmouth is the
largest in the world.
- Daily
inputs are of the order of Sinter 1100t: preheated Coke
400t.
- Blast
air is blown to the shaft at the rate of 57,000 Nm3/hr.
at 1000 degrees C (1400 -1500t): tuyere
injected secondary material 8t.
- The
basic process follows the reaction ZnO + CO = Zn + Co2.
- However
since this reaction is reversible at temperatures less than
907 degrees C the top of the furnace is maintained at 1000
- 1050 degrees C.
- Reversion
of zinc vapour, in the presence of CO2 back to zinc oxide
is avoided by the lead splash condenser.
- Zinc
vapour from the furnace passes into the condenser, where
fine droplets of lead (created by rotors splashing a pool
of molten lead,) dissolve the zinc.
- Lead from the condenser
is pumped through a launder where water-cooled immersion
coolers reduce the temperature from 560 to 430 degrees C.
- The zinc separates
from the condenser lead and the zinc is tapped into ladles
before being conveyed to the zinc refinery.
- The lead oxide
in sinter feed is reduced to lead in the furnace shaft and
is batch tapped from the hearth of the furnace, simultaneously
with slag.
- Lead is recovered
tighter with its Cu, Au
and Ag content as 4 tonne bullion
blocks.
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