AMMONIUM CARBONATE LEACHING OF CARBON STEELMAKING DUST - DETOXIFICATION POTENTIAL AND ECONOMIC-FEASIBILITY OF A CONCEPTUAL PROCESS

Dumping of untreated dust generated during electric arc furnace (EAF) carbon steelmaking is nowadays regarded as hazardous practice. This is due to the presence in the material of toxic species leachable under mildly acidic conditions. The use of ammoniacal ammonium carbonate (AAC) leaching for the treatment of EAF dust has been investigated on a laboratory scale and is reported in this paper. The experiments were conducted on dust samples from three European companies. As received, the dusts were found to be toxic when tested according to current US Environmental Protection Agency (EPA) toxicity testing procedures. Toxicity was on account of the leachability of one or more of the following: Ag, Hg, Pb, and Cd. For the three dust samples, it has been found that AAC leaching is able to rapidly solubilize the contained free zinc oxide to yield non-toxic residues according to EPA criteria. On the basis of the bench scale results obtained, a process is proposed for the treatment of EAF dust by ACC leaching. A preliminary economic appraisal of the proposed process is presented which indicates that AAC leaching has a potential of being a competitive alternative to current dust treatment technologies.