Outotec® Zinc Direct Leaching Process is a pioneering atmospheric leaching method for zinc concentrate.
Outotec process has demonstrated an overall zinc extraction of 98%, although the temperature is kept low, at about 100°C, and sulfuric acid concentration at 10-40 g/l. Oxygen is fed into the acidic slurry, which enables the leaching of the zinc from its sulfidic compound. Elemental sulfur is produced simultaneously in the reaction.
Outotec® Zinc Direct Leaching Process with atmospheric system has the following advantages:
- Simple reactor construction, little maintenance
- High availability
- High zinc recovery
- Steady production rate
- Easy to control
- Low power need
- No explosion risk
- No molten sulfur
- Low investment - 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. It is also possible to design the Zinc Direct Leaching Process as a stand-alone operation.
If necessary, the concentrate leaching stage can also include flotation cells for separating the sulfur material and iron residue, e.g. jarosite.
Further benefits of Outotec® Zinc Direct Leaching technology include:
- Flexibility with respect to various feed materials
- Possibility to use concentrate with low zinc content
- More environmentally-friendly zinc production thanks to efficient use of raw materials