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Outotec's Circulating Fluid Bed (CFB) roasting technology of gold bearing minerals is often the first step in the metallurgical process of gold recovery. Sulfur removal and carbon burning are essential and in some cases where arsenic is present, the latter has to be efficiently removed in order to obtain acceptable gold recovery in the subsequent calcine leaching step and to protect the environment.
Since the gold content of most ores is low, large amount need to be treated in order to ensure attractive economics. The goals of the roasting process are:
- High sulfur and carbon burn out
- High arsenic removal and/or fixation
- Uniform and precise temperature control
- Precise control of oxygen
- Safe and controlled combustion of additional fuel when required
- High throughput per roaster unit
- Efficient energy management
- High flexibility in ore range and capacity
Only the Circulating Fluid Bed (CFB) Roasting can operate within all of the above specific process requirements. The Features of our CFB Roasting process are:
- Suitable for a wide range of materials, ROM (run of mine) or concentrates
- Tailormade flowsheet
- Excellent process control
- Easy fuel addition
- High plant flexibility
- High gold recovery
Thanks to higher gas velocity than a stationary fluid bed has, the CFB technology provides the right conditions for efficient heat and mass transfer. Combined with extremely accurate process control, these advantages make for an ideal porosity of the calcine. Gold recoveries of 95 % and higher have been achieved in industrial operation for ROM and for concentrates.
Outotec is able to deliver the hole off-gas treatment and energy recovery system after the roaster which includes following process steps:
- Waste heat boiler
- Hot Electrostatic Precipitator (ESP)
- Wet Gas Cleaning
- Sulfuric Acid Plant
For further information please contact zinc(at)outotec.com
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