Coarse sludge (sample A) and fine sludge (sample B) from a Brazilian Linz Donawitz - LD steelworks integrated plant was characterized. Chemical analysis determined high level content of iron (51.54 - 77.53%) and lower grades of zinc (0.49 - 1.69%). XRD analysis permitted to observe various mineralogical phases, such as: metallic iron, wustite, franklinite, magnetite, portlandite, periclase, calcite, calcium oxide, silicon, moissanite-2H and srebrodolskite. Microscopic Optical and Scanning Electron Microscopic studies shown morphologies of these residues were made up of globular and skeletal aggregates of metallic iron intergrown with crystals of iron oxides especially wustite and a significant presence of calcite and calcium oxide in spherical nodes having particle sizes between 0.12 and 0.15 mm. Scanning Electron Microscopy - Energy Dispersive X-ray spectroscopy studies denoted significant contain of Fe, O and Ca in both samples. In addition, a thermogravimetric analysis by DTG-DSC-TG at 1000° C exhibited a mass loss of 97.43% for the sample A and 92.57% for the sample B.
Keywords: Linz Donawitz-LD, LD converter, BOF converter, Steel sludges, Converter process