Typical process of zinc hydrometallurgy consists of zinc concentrate roasting, calcine leaching, electro-winning, ingot casting and acid-making.

Zinc leaching is performed in diluted sulfuric acid system or ammonium system. The leaching acidity, temperature and pressure are regulated to achieve the most optimal zinc leaching rate. The pregnant leaching solution (PLS) has to be thickened and filtrated to remove leaching residue and purified to get qualified zinc electrolyte. Zinc cathode is produced through electrowinning and then molten and cast into standard ingot.

Zinc leaching process plays a big role in zinc hydrometallurgy for its importance to recovery rate. Several approaches are available to serve for different leaching conditions, as shown in the table.

Zinc sulfide concentrate can be directly charged for acid leaching or getting roasted before acid leaching. Zinc oxide concentrate, crude zinc oxide (C.Z.O.) or zinc flue dust from EAF can be leached by ammonium chloride which can tolerate high F/Cl content materials.

Depending on the variety of raw material for leaching, different leaching methods are taken such as ammonium leaching, conventional acid leaching process, hot acid leaching process, ZPL process, etc..

Treatment methods of leaching residue also varies. Leaching residue from conventional leaching is treated by Waelz kiln; and goethite precipitate via iron removal  can be recovered to standard iron ore through flash magnetization roasting furnace; high silver and lead bearing leaching residue can be treated by side-blowing furnace for silver and lead recovery.

The whole view of zinc metallurgy can hardly be given in a passage because of process varieties and complex . Based on clients’ leaching test result, capacity plan and actual plant condition, Metalcess can provide tailored process and the most suitable equipment.