Fused Calcium Aluminate Production from Aluminum White Dross Residue

Despite the numerous advantages of using and recycling aluminum, inevitable by-products in the form of non-metallic residues (NMR) of aluminum white dross (AWD) can be environmentally harmful. The aim of this study was to find a solution regarding aluminum treatment via pyrometallurgical methods and, ultimately, to obtain calcium aluminate (CA) flux for the iron and steel industries. The optimum parameters, such as temperature, duration, and particle size of the limestone, for CA production from the NMR of AWD were investigated. Calcination experiments were divided into two categories. The aim of the first set of experiments was to increase alumina (Al₂O₃) purity and remove nitrogen (N) in the rotary furnace. N content was reduced to 0.25 wt% at 1150 °C and 2 h duration, while Al₂O₃ purity reached 94.67 wt% as the optimum results for the calcination experiments. The obtained results were also compatible with thermodynamic simulations. In the second set of experiments, NMR of AWD was synthesized via the addition of limestone to obtain CA. It was observed that the crushed limestone favors the forming of CA phases. Last, in order to determine the optimum fusing condition, the fusion process was applied 1350, 1450, and 1550 °C to mixture of limestone and NMR. It was observed that the material completely melted at 1550 °C and phases containing CA were formed. The produced samples were characterized by X-ray diffraction (XRD), atomic absorption spectroscopy (AAS), and N analyzer. Graphical Abstract: [Figure not available: see fulltext.]