Zinc leaching residue, either from conventional zinc leaching or high acid zinc leaching, usually contains zinc, lead, indium and precious metal, which are of great value to recover. It is also considered as hazardous solid waste from zinc leaching process.

When the zinc leaching residue contains relative high lead and silver, waelz kiln is no longer the solution. In this case, high lead and silver content are re-collected in the fuming dust. The fuming dust then has to be re-leached. Silver and lead are recycled in the repeated leaching & precipitate & fuming process. Actually, Silver gets lost in the recirculation, and recirculation of lead cause unnecessary energy consumption. 

Metalcess provides an effective solution with short process targeting at treating high lead & silver leaching residue. 

This solution involves two oxygen-enriched side-blowing furnaces for smelting and fuming respectively. Press-filtered high lead & silver leaching residue can be directly charged into the side-blowing furnace for smelting. Lead and valuable metal is reduced into metallic status and are enriched into lead bullion or copper matte for further recovery. Zinc reports into slag and then is charged into the secondary side-blowing furnace for fuming. In practice,  the overall silver recovery rate > 90%, the slag from the first furnace contains lead <2%, silver <10ppm. The fuming slag from the secondary furnace contains lead <0.5%, zinc <1% and silver<10ppm. The fuming slag is safe for landfill. 

Both furnaces apply oxygen-enriched air and use crushed coal as fuel and reduction agent. This solution allows lead/silver separation from zinc to avoid silver loss and lead being locked in the circle, of high ROI. The process is adjustable to different capacity level.