(MERAF) for the Base Metals Smelting Sector - CCME

3.2.2.7. Ammonia sulphate recovery
Ammonium sulphate crystals are recovered from the barren liquor in a series of
crystallizers. The crystals are then fully dried in dryers. The gases then exhaust
to the atmosphere via a stack. The sulphate product is sold as fertilizer. The
evaporated water is condensed and recycled to the process or disposed of in the
effluent sewer.
Intermittently, solution is purged from the feed tank to remove excess chlorides
from the system.
The water collected in the well for the condensers (commonly known as Hotwell)
is recycled and used in a number of locations. The excess is discharged to the
storm pond so that it can be treated to remove its ammonia content.
3.2.2.8. Ammonia recovery
Ammonia which is recovered as a solution from the other circuits is distilled in
Ammonia Recovery and then recycled.
Ammonia laden atmospheric vent gases from the Copper Boil circuit and Leach
circuits are scrubbed with water in the Vent Gas Scrubbers. The ammonia
present in the vent gases are absorbed by the water. The scrubbers vent to the
atmosphere and the resulting ammonia water solution is sent to the aqua storage
sphere.
Ammonia laden pressurized vents from the leach autoclaves are scrubbed with
water in the Tail Gas Scrubbers. The ammonia present in the vent gases is
absorbed by the water. The scrubbers vent to the Still Bottoms Evaporator and
the resulting ammonia water solution is sent to recycle storage.
The ammonia rich vents from Cobalt Separation and some Cobalt Conversion
and Reduction vents are scrubbed with water in the Cobalt Separation scrubber.
The ammonia present in the vent gases are absorbed by the water. The
scrubber vents to atmosphere and the resulting ammonia water solution is sent to
the recycle storage.
Solution from storage is pumped into the High Pressure Still. In the still, the
solution is heated and the ammonia is evaporated. The ammonia is condensed,
stored in an ammonia storage drum, prior to re-use. The resulting liquid stream
is pumped to the Still Bottoms Evaporator and is reused in the process.
The Tail Gas Scrubber vent gases and the High Pressure Still liquid stream enter
the Still Bottoms Evaporator. In the evaporator, some of the water is evaporated
and vented to the atmosphere. The resulting evaporator bottoms solution is
reused by the process.
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