The Waelz Furnace Procedure

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Dusts, sludge's, filter cakes and other zinc containing wastes, supplied by our clients in different compositions, are initially stored in closed silos or covered boxes. The intermediate storage capacity is equivalent to approximately one to two months' of production, depending on the facility. In the first stage, these raw materials are mixed and pelletised with water, coke and lime to guarantee a homogenous feeding of the waelz kiln. The so-called micro-pellets are fed into the furnace either directly or via an intermediate storage. At kiln operating temperatures of approx. 1,200°C all volatile elements, mainly zinc, are transformed into the gas-phase. There they are oxidised to form the so-called waelz oxide, which is rich in zinc oxide. By the off-gas treatment facilities the waelz oxide is recovered and sold afterwards to the zinc industry as a secondary feed material.

The waelz plants at Befesa Zinc Aser and Befesa Freiberg are using the so-called second- respective triple-leach-process to purify the waelz oxide.

The produced slag can be used as a construction material for roadbuilding at landfill sites. In Spain it is used under its brand name Ferrosita® as a natural drying agent or as a filling material for the construction industry.