Processing of electric arc furnace dust via chloride hydrometallurgy

Abstract

Production of steel in the electric arc furnace (EAF) generates a dust byproduct containing non-ferrous metals. In particular, zinc, lead and cadmium are volatilized at steelmaking temperatures and report as oxides or ferrites in the dust collected from EAF off-gas. Direct recycle of dust is impractical, while — in North America at least — disposal in secure landfills is becoming prohibitively expensive.

The paper presents the results of a phased process development program for the treatment of this dust, including:

• preliminary scoping/process definition study

• laboratory scale testing of key unit operations

• preliminary feasibility study

The first stage of the process sequence is atmospheric leaching of EAF dust with a ferric chloride solution: 2 FeCl₃ + 3 MO + H₂O → 2 FeO•OH + 3 MC1₂ (M = Zn, Pb, Cd, etc.)

The slurry product is then treated in an autoclave under conditions that result in formation of a free-settling, filterable residue consisting mainly of hematite and silica. Results of hot CCD and filtration/washing tests indicate that the residue meets USEPA and Canadian criteria for disposal in sanitary landfills. Possibilities for alternate uses of residue are also discussed.