Abstract
Massive hematite ore (MHO) is a special high-grade iron ore, used as lump ore in the process of obtaining direct reduction iron (DRI). The influence of porosity on the reducibility of MHO from the Capitão do Mato Mine (Iron Quadrangle, Brazil) was investigated using optical and scanning electron microscopes on drill core and open pit samples. Hematite is the main component of the samples and occurs as granular crystals (10 mum), microplates (1 mum) and euhedral martite (10 to 30 mum). Quartz, maghemite, kenomagnetite and goethite are minor components. Primary micropores (Å to 1 mum) are associated with microplaty crystals that fill cavities between granular hematite. Secondary micropores (Å to 5 mum) related to euhedral martite crystals, are the most important. The total porosity of weathered samples, measured using nitrogen adsorption and mercury injection, attains values up to 11%, whereas unweathered samples have a porosity less than 2.5%. Reducibility is strongly enhanced by porosity, but inhibited by structure (bedding).
Highlights
For many years, iron ores were classified only by their chemical composition
The direct reduction (DR) process, used to obtain the direct reduced iron (DRI), is defined as any process in which metallic iron is produced by the reduction of iron ore below the melting temperature of any mate
The aim of this paper is to present results of the investigation of the microporosity of a particular banded iron formation (BIF) iron ore, known as ‘‘hematita compacta’’ from the Capitão do Mato Mine, Iron Quadrangle, Minas Gerais State, Brazil (Figure 1)
Summary
Iron ores were classified only by their chemical composition. In addition to the Fe2O3 content, the quality of the ore was defined by its contents of P2O5, SiO2, Al2O3, and loss on ignition (LOI). The steelmaking industry requires additional data on physical properties (size-range, fines, mechanical strength), metallurgical properties (reducibility, swelling, clustering or sticking and Reducibility is defined as the measure of the rate at which a given iron ore or agglomerate will reduce under arbitrary and fixed temperature and gas composition (Feinman and MacRae 1999). The demand for DRI continues to increase due to its multiple application in the steel industry, including electric arc and basic oxygen furnaces (Kopfle 1999)
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