Impurity behavior in low-temperature sintering products of ironmaking dust in the presence of ammonium chloride

Abstract

In this study, the elemental composition of dust from the melting of scrap metal in an electric arc furnace was analyzed using an X‑ray fluorescence energy dispersive spectrometer (RLP-21) to determine the concentrations of impurities at their lower detection limits. A wide range of impurities was identified in the dust: Cu, Fe, Ti, Cr, Ni, Cd, Mn, Sn, Si, Ca, K, S, Cl. Using the Olympus BX51 microscope, new data on the forms of impurities in dust have been obtained. It was shown that impurities in the dust are present in the form of oxides. Based on the new results, a thermodynamic analysis of the reactions between dust components and ammonium chloride under low-temperature sintering conditions (573–1073 K) was performed. It was found that almost all impurities, except chromium, concentrate in the clinker as solid oxides during the sintering process. A high potential for the removal of titanium and tin as gaseous chlorides in the vapor phase was identified. Laboratory experiments were conducted on sintering dust with NH4Cl under optimal process conditions (temperature—773 K, NH₄Cl consumption—1.5 times the stoichiometric amount required for lead chlorination, sintering time—60 min). Based on these experiments, the quantitative proportions of impurities in the resulting clinker were determined. It was found that during sintering tin and titanium are volatilized in significant amounts (more than 30% of their total content in the initial dust). The results obtained are fundamental for the development of selective lead extraction technology from dust. They will be used to develop an integrated chlorination process for the treatment of ironmaking dust with selective recovery of valuable metals into marketable products.