Metallurgical resource recovery from waste steelmaking slag from electric arc furnace

Steel slag from an electric arc furnace (EAF) may contain significant amounts of oxides of valuable metals. The recovery of iron and other metals from the EAF slag using smelt-reduction process was studied with coal as the reductant. A pig iron phase with high carbon and a final slag depleted of the valuable metals were generated. SEM-EDS and ICP analysis indicated that valuable metals could be successfully recovered in the pig iron. Nearly 84% recovery of Fe was observed with about 85%, 95% and 84% recovery of Mo, Ni and Co, respectively. In addition, 48% Cr, 30% V and 7% Mn were also recovered with a total metal yield of about 20%. An experimental design was developed using the three most important process variables, dwell time, reaction temperature and basicity, with a view to optimize the process and identify the most favourable process conditions. A total of 15 experiments were carried out per the Box-Behnken design using Response Surface Methodology. The response variables included metal yield, total yield, slag yield, Fe recovery, Cr recovery, Mo recovery as well as C and S content of the metal. Statistically significant empirical models for the response variables were developed and the process was optimized. The optimum was obtained at a dwell time of 20 min, reaction temperature of 1681 K and basicity of 1.025. The recovered pig iron with 3.32% C and 0.1% S is suitable for use in steelmaking as hot metal. The final slag may be used in construction applications.