TRAIL, British Columbia Four years of hard work by researchers at TECK COMINCO is paying off. They have developed a new, low-cost hydrometallurgical process for the direct extraction of zinc from sulphide ores. Known as the HydroZinc process, it involves heap leaching with naturally-occurring bacteria, followed by neutralization, solvent extraction, and electrowinning.
A demonstration run of the process was completed last year using 10,000 tonnes of agglomerated sulphide ore from the Red Dog mine in Alaska. The ore was placed in two pads, one of which was operated in halves and the other by quadrants, with drip emitter irrigation systems. The ore graded 15.2% Zn, 5.5% Fe, 4.9% Pb, and 14.4% S. Leachate from the pads was neutralized in three rubber-lined reactors. Then it was clarified and filtered, creating feed for the solvent extraction plant and a gypsum/ferric residue. From the 10,000 tonnes of agglomerated sulphide ore, 450 tonnes of zinc was recovered.
Teck Cominco researchers have taken the results of their demonstration and created a case study for the potential development of a HydroZinc plant. The outcome of their studies is available at www.teckcominco.com in the form of a .pdf presentation.