Today, steel scrap recycling is of great significance as a crude steel source to preserve natural resources and protect the environment. Our customers use Electronic Arc Furnace to recycle steel scrap to produce new steel. In this process, a hazardous waste called “steel dust” is generated. Befesa services and recycles this hazardous waste.
Compared to the classic Waelz process, the patented SDHL Waelz process, applied at the five production sites in Spain (Befesa Zinc Aser S.A.U., Asua-Erandio), in Germany (Befesa Zinc Duisburg GmbH, Befesa Zinc Freiberg GmbH), in South Korea (Befesa Zinc Korea, Ltd.), in Turkey (Befesa Silvermet S.L., Iskenderun) and in France (Recytech S.A., Fouquières-les-Lens), has been acknowledged as the best available technology (BAT) thanks to the numerous benefits it offers.
The SDHL Waelz process is composed of the following process steps (cf. Fig.):
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 pelletized with water, coke and lime to guarantee a homogenous feeding of the Waelz kiln. The 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 and re-oxidized to Waelz oxide. By the off-gas treatment facilities the Waelz oxide is recovered and provided afterwards to the zinc industry as a secondary feed material.
By adding air to the charge at the end of the kiln, most of the iron reduced in the process is reoxidized to iron oxide (FeO). The heat of oxidation generated is used to preheat the entering fresh air and thus supplies the thermal energy required for the chemical processes in the reaction zone. Thanks to the proprietary development of this so-called SDHL process, it was possible to distinctly optimize efficiency compared to the classic Waelz process.
The plants Befesa Zinc Aser, Befesa Zinc Freiberg and Befesa Zinc Gravelines are using the double- respective triple-washing-process to purify the Waelz oxide.
The produced slag can be used as a construction material for e.g. road building. In Spain it is used under its brand name Ferrosita®.