Steel making dust recycling: melting behavior and interactions with refractory bricks

Stainless steel production generates significant quantities of flue dusts, which are considered as hazardous waste in most industrialized countries as they contain harmful elements, such as heavy metals. On the other hand, the dusts also contain valuable metals, such as steel alloying elements, but the recovery of the valuables is difficult due to the complex composition of the dusts. In this work, the melting behavior of dusts from an Electric Arc Furnace and an Argon Oxygen Decarburization converter were investigated at temperatures 800-1400 °C. In addition, the interaction between a synthetic dust, with high concentrations of potassium, fluorine and chlorine, and selected refractories was studied at 1300 °C mimicking the freeboard conditions of a dust smelting furnace. Melting of the EAF dusts begun in the temperature region of 1250-1300 °C depending on the composition, whereas AOD flue dust, because of its high fluorine content, had a melt fraction of approximately 30 % already at 1200 °C. The present experiments showed that magnesia has good corrosion resistance against potassium vapors at 1300 °C and the penetration depth of potassium into chromium-containing refractory materials was limited to the vicinity of the contact surface. In addition, alumina-silicate refractories seem to be more susceptible to volume expansion than the other refractories studied, causing cracks through which potassium vapors can easily penetrate deep into the refractory lining.