Co-utilization of converter sludge-containing dedust wastewater in iron ore sintering to save fresh water, enhance quality and reduce pollution

Due to the high proportion of the steel output produced by oxygen converter, significant quantities of converter sludge (CS) and dedust wastewater (DW) are generated annually as waste materials. This study tries to achieve the co-utilization of converter sludge-containing dedust wastewater (CSDW) in iron ore sintering to save fresh water and emission reduction. Firstly, this study quantitatively characterized the mineralogical characteristics of the CS through X-ray diffraction (XRD-Rietveld) and scanning electron microscope (SEM-EDS). The results indicated that the iron oxides wrapped the metallic Fe, and other impurities such as CaO, MgO and ZnFe2O4 mixed in the way of physical accumulation. The mineral composition of CS was metallic iron (9.2%), wustite (47.5%), calcium carbonate (31.7%), magnesium ferrite (4.8%), and zinc ferrite (6.7%). Influence of CSDW concentration on the granulation performance and sintering indexes was systematically studied through a series of experiments. Research findings showed that the permeability firstly raised from 9.66 to 12.88 JPU and then reduced to 11.94 JPU, and reached the maximum when the CSDW concentration was 40%. Migration behaviors of harmful elements Zn, K, Na, and Cl have been studied based on experiments and thermodynamic calculations. Cl in DW plays an important role in promoting the removal of alkali metals. The catalytic mechanism can be summarized as the reaction of HCl, Cl2 and alkali metal oxides (Na2CO3, K2CO2, NaAlSi2O2, and KAlSi2O2) to form NaCl and KCl. With this technology, the removal rate of ZnO, K2O, and Na2O increased from 23% to 74%, 13%–42%, 1%–34%, respectively. This study aims to propose a new method for the co-utilization of CSDW in iron ore sintering, which would be helpful to save fresh water and reducing emissions in the iron and steel industry.