Mineralogical characteristics, metallurgical properties and phase structure evolution of Ca-rich hematite sintering

Abstract

In order to study the sintering characteristics of Ca-rich iron ore, chemical analysis, laser diffraction, scanning electron microscopy, XRD-Rietveld method, and micro-sintering were used to analyze the mineralogical properties and sintering pot tests were used to study the sintering behavior. In addition, a grey correlation mathematical model was used to calculate and compare the comprehensive sintering performance under different calcium-rich iron ore contents. The results demonstrate that the Ca-rich iron ore has coarse grain size and strong self-fusing characteristics with Ca element in the form of calcite (CaCO₃) and the liquid phase produced by the self-fusing of the calcium-rich iron ore is well crystallized. Its application with a 20wt% content in sintering improves sinter productivity, reduces fuel consumption, enhances reduction index, and improves gas permeability in blast furnace by 0.45 t/(m²·h), 6.11 kg/t, 6.17%, and 65.39 kPa·°C, respectively. The Ca-rich iron ore sintering can improve the calorific value of sintering flue gas compared with magnetite sintering, which is conducive to recovering heat for secondary use. As the content of the Ca-rich iron ore increases, sinter agglomeration shifts from localized liquid-phase bonding to a combination of localized liquid-phase bonding and iron oxide crystal connection. Based on an examination of the greater weight value of productivity with grey correlation analysis, the Ca-rich iron ore is beneficial for the comprehensive index of sintering in the range of 0–20wt% content. Therefore, it may be used in sintering with magnetite concentrates as the major ore species.

Keywords

calcium-rich iron ore / mineralogical properties / phase structure evolution / flue gas heat / grey relation analysis

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