Hydrometallurgical Treatment of Steelmaking Electric Arc Furnace Dusts (EAFD)
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I.
INTRODUCTION
THE steel available in the market is mainly produced by blast furnace and electric arc furnace (EAF). On average, the production of one metric ton of steel results in 200 kg (in electric arc furnace steelmaking) to 400 kg (in blast furnace steelmaking) of by-products (slags, dusts, sludges, and other materials).[1–3] During the meltdown of scrap, the electric arc furnace (EAF) can reach temperatures of 1873 K (1600 °C), and many components of the charge, including zinc, lead, and cadmium are volatilized. Especially in cases where galvanized scrap is used in the EAF, most of the zinc from the steel scrap ends up in the dust and fume because of its very low solubility in molten steel and slag. Zinc vapor and other gaseous compounds react in the gas-cleaning system generating compounds such as ZnO and ZnFe2O4. During the production of steel from scrap in EAF, from 10 to 15 kg/ton of charge are recovered in the gascleaning units as dust. The main components of the electric arc furnace dust (EAFD) are Fe, Zn, Ca, Cl, and Pb, with small concentrations of Cd, Mg, Na, and other elements. The disposal of this waste has become a serious problem in recent years. The world generation of EAFD is estimated to be around 3.7 million tonnes per year. Plants from Europe generate around 500,000 and 900,000 tonnes of dust per year.[4] In Greece, all the five steel factories are scrap-recycling facilities, where more VICTOR MONTENEGRO, Researcher, PASHALIS OUSTADAKIS, Chemical Engineer, Senior Researcher, PETROS E. TSAKIRIDIS, Chemical Engineer, Senior Researcher, and STYLIANI AGATZINILEONARDOU, Professor, are with the Laboratory of Metallurgy, School of Mining and Metallurgical Engineering, National Technical University of Athens, 9, Iroon Polytechniou Street, 15780, Zografou, Athens, Greece. Contact e-mail: [email protected] Manuscript submitted February 14, 2013. METALLURGICAL AND MATERIALS TRANSACTIONS B
than 30,000 tonnes of EAFD are produced annually.[5] Owing to its chemical and physical properties, the EAFD has been categorized as hazardous waste according to the European Waste Catalogue (EWC 2002).[6] As a result, the disposal of these industrial solid wastes could cause environmental risk, whereas EAFD recycling could prevent landfill waste, reduce emissions, and help in preserving the natural resources. The processing of EAFD has not been changed drastically in the recent years. In general, the process treatment for EAFD aims mainly at the recovery of zinc, which is commonly used in the galvanizing process of carbon steel. Pyrometallurgical methods require high temperatures and reducing agents to produce metal oxides. The Waelz Kiln technology is widely used for the EAFD treatment. Around 80 pct of the recycled EAFD is processed by this method, which is of the few options for dust treatment at commercial level.[7,8] The Waelz rotary kiln requires significant investment, and it is financially attractive for treatment of dust with 15 through 20 pct Zn and plant capacities of at least 50.000 t/a.[9] The Imp
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