Green and efficient utilization of stainless steel dust by direct reduction and self-pulverization

Stainless steel dust is a solid waste and contains a large number of valuable Fe, Cr, and Ni metal oxides, which should be recovered efficiently. Through direct reduction and self-pulverization separation, the goals of high metal recovery ratios and grades in the new process of comprehensive stainless steel dust utilization were achieved. Combined with theoretical analysis and experimental research, the effects of different conditions (FC/O ratio, reduction temperature, reduction time) on the reduction process and self-pulverization of reduction products were studied. The results showed that the optimal FC/O ratio was 0.8, reduction temperature was 1450 °C and reduction time was 20 min for the metal oxides in stainless steel dust to be completely reduced by carbon-thermal reduction; the self-pulverization holding temperature was 1100 °C, the holding time was 15 min, the conversion ratio of Ca₃SiO₅ to Ca₂SiO₄ reached the maximum, the content of γ-Ca₂SiO₄ in the reduced slag after cooling was increased, and a higher degree of self-pulverization was achieved. Fe-Cr-Ni-C alloy with an iron grade of 66.82%, chromium grade of 20.02% and nickel grade of 4.12% was manufactured successfully from stainless steel dust. The recoveries of iron, chromium and nickel in the stainless steel dust were 92.50%, 92.02% and 93.74%, respectively.