Zinc Calcine Leaching

Enable efficient zinc and by-product recovery from the calcine produced in zinc sulfide roasting with Outotec's zinc calcine leaching process. The optional Outotec pure jarosite precipitation gives remarkably higher recoveries of zinc, silver, and lead than traditional calcine leaching processes.

Benefits

Recovers zinc as an SHG ingot and by-products such as Pb, Ag, Cu, Cd, Co, Ni, In, Ga, and Ge
Offers a total zinc plant solution together with Outotec's fluidized bed roasting and acid plant technologies
Can be easily customized according to by-product recovery demands
Enables the total recovery of Pb and Ag in the hydrometallurgical circuit and a higher recovery of zinc than in a standard jarosite process with the Outotec pure jarosite precipitation solution

Zinc calcine leaching

Zinc calcine produced in roasting contains zinc oxide and zinc ferrite. In order to obtain the maximum amount of high-quality zinc, the two must be leached in different conditions. Firstly, zinc oxides are leached in neutral leaching stages, during which ferrites do not dissolve. The residue of neutral leaching is led to the second leaching stage, which uses higher acidity and temperature. For this step, Metso has two options.

If the lead and silver content of the zinc calcine is high, the residue of neutral leaching can be leached in the Metso hot acid leaching process. The incoming zinc ferrite is leached, guaranteeing an overall high level of zinc recovery. A leaching by-product is produced simultaneously with the highest possible lead and silver content. The silver can then be further recovered as silver concentrate using Metso flotation technology.

For low lead and silver content, the Metso conversion process can be utilized. In this process, the zinc ferrites are leached simultaneously with the precipitation of jarosite.