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Outotec process has demonstrated an overall zinc extraction of 98%, although the temperature is kept low, at about 100°C, and sulfuric acid concentration 10-40 g/l. Oxygen is fed in the acidic slurry, which enables the leaching of the zinc from its sulphidic compound. Elemental sulfur is produced in simultaneously in the reaction.
In spite of lower reaction rate, the atmospheric system has the following advantages compared to leaching in elevated pressure and temperature:
- Simple reactor construction, little maintenance
- Easy to control
- Low power need
- Low investment
- No explosion risk
- No molten sulfur
It is cheaper to build a process with large reactor volumes than with autoclaves.
The concentrate direct leaching can be easily integrated with calcine leaching. This gives an opportunity to feed the "well leaching" zinc concentrate to the direct leach process and the balancing amount to the roaster. Keeping the roasting department at full capacity offers a flexible way to process different zinc concentrates in the most economical way.
If needed, the concentrate leaching stage can also include flotation cells for separating the sulphur material and iron residue, e.g. jarosite.
It is also possible to design the Atmospheric Direct Leach Process as a stand-alone operation.
For further information, please contact  zinc(at)outotec.com
Brochure
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