Green and efficient recovery of stainless steel dust by iron-bath direct reduction

Abstract

In this study, valuable Cr and Fe in stainless steel dust (SSD) were extracted and then recycled for industrial production. The basic laboratory experiments on the direct reduction of SSD by molten iron were conducted to study the reduction mechanism of Cr2O3 during the recovery of SSD in the iron bath process. A reaction model was established to investigate the variation in material transport in the boundary layer during the reduction of Cr2O3. The phase components, micromorphology, and chemical composition of the experimental raw materials and samples were analyzed by X-ray diffraction, scanning electron microscope–energy dispersive spectrometer, inductively coupled plasma–mass spectrometry, and carbon–sulfur analyzer. The experimental results showed that Cr2O3 and FeO combined in SSD could be reduced by C in molten iron, and that the reduction of FeO occurred before that of Cr2O3. The C and Cr contents in molten iron varied with experimental time in parabolic and cubic polynomial forms, respectively. At 1823 K, the reduction ratios of Cr2O3 and FeO after 35 min reached their highest values of 73.03 % and 90.76 %, respectively. Based on theoretical and experimental analyses, a recovery process was developed to recycle the dust generated during stainless steel smelting for its own production. This process can continuously absorb SSD without any complex equipment and is expected to completely mitigate the environmental impact caused by the presence of SSD.