Development of a novel process for energy and materials recovery in steelmaking slags

Abstract

This work aims at gathering fundamental knowledge for the development of a novel process for energy (H₂ gas) and materials (magnetite Fe₃O₄) recovery in hot-steelmaking slags by reacting molten steelmaking slag with steam. Thermodynamic simulation was carried out to calculate the accumulated amount of produced H₂ gas as a function of the volume of H₂O–Ar gas introduced and the precipitated phases of the molten slags during controlled cooling. Laboratory experiments of crystallization behaviours of molten slags during cooling were visualized in situ through a confocal laser scanning microscope, and the cooled slags obtained were characterized by using SEM-EDS and XRD. CCT diagrams for different slags were created showing the slag crystallization/phase transformation at different cooling rates. The recovery ratio of H₂ gas and the maximum potential recovery ratio of iron oxide in the oxidized slags were calculated, which concludes that with increasing the slag basicity from 1.0 to 1.5 and 2.0, the recovery ratio of H₂ was found to increase from 12.6 to 23.7% and 22.6%, and the maximum potential recovery ratio of iron oxide was found to increase from 18.3 to 34.4% and 32.8% under the investigated conditions.