The recovery of zinc oxide from low grade zinc-bearing material by Waelz kiln is a popular and economic method. The furnace can treat various zinc material such as low grade zinc oxide ore, zinc leaching residue, zinc-bearing water quenched slag from lead smelting, zinc electrolyte purification precipitate, zinc dross from coating production, blast furnace flue dust, low grade refractory smithsonite and other zinc-bearing waste with fluorine and chlorine, etc.

Working Principle
The raw material at dry basis is proportioned with 40-50% fuel (coke or pulverized coal). The mixture is transferred by belt conveyor to the charging port at the end of the kiln. In the Waelz kiln, temperature approx. 1000-1300 °C, the metal compounds react with carbon-based fuel or carbon oxide, get reduced to metallic status, evaporated and later oxidized (to ZnO, PbO, In2O3, GeO2, etc.). These oxides are collected in the dust collection system. Halides from the raw material also report to flue dust. Cooling of flue gas is done step by step to collect metal oxides and halides separately.

Compared with traditional waelz kiln, Metalcess made improvements to extend the high temperature zone to achieve even temperature distribution, greatly reducing the probability of ring-formation and kiln body damage. By extending the high temperature zone, the hot point temperature will be reduced, thus prolong the service lifetime of refractory lining from 3 months to 6 months. In the meantime, we changed the way of coal utilization, reducing coal percentage to 40% below, which saves the operation cost.

Characteristics 

1. Waelz process can recover valuable metals from smelting slag, leaching residue and flue dust, reducing solid waste emission and its impact to environment.
2. The recovery valuable metals like Zn, Pb, In by Waelz kiln are highly efficient.
3. Waelz process can also be used for the removal of fluorine, chlorine & arsenic from zinc flue dust.