Recherche de protocoles de valorisation des poussières d'aciérie électrique par voie hydrométallurgique

Abstract : Production of steel in the electric arc furnace generates a dust by-product containing non-ferrous metals. Due to the presence of significant amounts of leachable compounds of zinc, lead, cadmium, chromium and nickel , EAF dust is classified as hazardous waste. The quantity of EAF dust generated per year around the world represents a possible recovery of 910 000 tons of zinc. The objective of the process studied is to extract zinc and lead from EAF dust without destroy iron oxides matrix which can be recycle to the steel industry. The major mineralogical forms present in these waste are Fe3O4, ZnO, ZnFe2O4, PbOHCl. The process consists in an hydrometallurgical treatment of waste based on selective leaching of zinc and lead. At first, a leaching is carried out with a chelating agent, the nitrilotriacetate anion N(CH2-COO)3 [exposant]3- (NTA exposant]3), used under the protonated form HNTA [exposant]2-. The treatment of different EAF dust samples during an hour at room temperature with a molar solution of reagent allows the total leaching of ZnO. Iron level does not exceed 3 % in mass. The recovery of zinc and lead is performed by precipitation of metallic sulphides with a solution. The normalized leaching procedure AFNOR X31-210 applied to the leaching residues shows that all the samples meet acceptance tresholds in specialised landfill. However, the residues contain an important amount of zinc under ZnFe2O4 form. The extraction of the element requires the destruction of the ferrite structure. For this, ZnFe2O4 is treated by FeCl3, 6 H2O. The reaction consists in a particles exchange O [exposant]-2 / Cl [exposant]- allowing the recovery of zinc under ZnCl2 form and iron as hematite Fe2O3. The separation of this both products is obtained by simple aqueous leaching. The whole zinc is extracted for a treatment at 150°C. Ultimate solid residues, which have been concentrated in iron, can be orientated towards steel industry
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Nathalie Leclerc. Recherche de protocoles de valorisation des poussières d'aciérie électrique par voie hydrométallurgique. Chimie. Université Paul Verlaine - Metz, 2001. Français. ⟨NNT : 2001METZ005S⟩. ⟨tel-01775455⟩

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