EUROPEAN STEEL TECHNOLOGY AND APPLICATION DAYS 2017 - ESTAD 2017

The steel production via the EAF route produces free lime containing dust. In the case of carbon steel production, the main dust recycling process is the Waelz furnace, allowing the recovery of zinc but not of Fe. In the case of stainless steel production, the recovery of valuable alloying elements (a.o. nickel, chromium, and molybdenum) can be achieved by recycling the dust in the form of self-reducing briquettes into a liquid steel bath. A hydration step is mandatory before the briquetting of free lime bearing dust in order to avoid swelling and degradation of the produced briquettes. The amount of added water must be well controlled in order to ensure the full hydration and also to limit the residual humidity to avoid the need for a subsequent drying step. A straightforward methodology for the determination of the free lime content and of the water amount to be added has been developed and validated. Hydration trials have been carried out to study the respective impacts of the dust nature, the temperature and added water on the reaction kinetics. Industrial trials have confirmed that the behaviour is the same at pilot and industrial scales.