Optimal Recovery of Iron Values from a Low Grade Iron Ore using Reduction Roasting and Magnetic Separation

Textural complications of banded iron formation and the potential production of nano-magnetite: a case study from the Central Eastern Desert of Egypt

The current work makes integrated value-added, geological and chemical studies on the texturally intricate banded iron formation "BIF" that is represented here, as a case in point, by the Um Nar BIF located in the Central Eastern Desert of Egypt. Geologically, the Um Nar BIF is composed mainly of oxide-rich facies and silicate-rich facies mostly expressed as bands of variable thickness (90-730 µm). Magnetite, martite, goethite, and quartz are detected as the main components of the oxide-rich facies, while epidote, stilpnomelane, and garnet occupy the other facies type. The studied ore can be classified as a low-grade iron ore containing 51.23 wt.% Fe2O3 and 39.64 wt.% SiO2 along with considerable phosphorous content (1.01 wt.% P2O5). These elemental concentrations do not match the recommended benchmarks for iron and steelmaking (e.g.75.78-95.8 wt.% Fe2O3, 5-7 wt.% SiO2, and 0.04 wt.% P2O5). Moreover, the studied BIF has a poor liberation behavior on crushing and grinding due to the complex interlocking of magnetite with quartz and stilpnomelane expressed as a sieve-like texture. This textural complication directed the current work to investigate the potential exploitation of the Um Nar BIF as a precursor of nano-magnetite that is commonly synthesized by ferrous and ferric chlorides. Accordingly, HCl-based agitation leaching followed by co-precipitation was carried out, resulting in ultrafine mesoporous nano-magnetite (2.47-4.27 nm particle size, 120 m2g-1 surface area, 0.55 cm3g-1 pore volume, and 4.88 nm pore diameter) expected to serve in water treatment as an effective adsorbent for heavy metals.

Review on the chemical reduction modelling of hematite iron ore to magnetite in fluidized bed reactor

Steel production is considered as one of the major backbones of many economies. Though blast furnace is the primary route of steel production, the industries are willing to alternatives technologies such as the high temperature-controlled conversion of hematite to magnetite. The geological and mineralogical characteristics of the low-grade iron ores possess difficulties in their conventional enrichment. The literature concludes the advantages of high-temperature conversion in terms of easiness in downstream operations caused by decreased hardness and increased magnetic susceptibility of magnetite. The modelling work has been primarily focused on the direct reduction of iron ore to metallic iron. The present compilation discusses the scientific and engineering developments on the reduction-roasting of iron-ore followed by the CFD–DEM modelling and simulation work performed to reduce iron ore to magnetite. It provides a comprehensive review of the experimental and industrial progress done in the area.

Red Mud as a Secondary Resource of Low-Grade Iron: A Global Perspective

Managing red mud (RM), a solid waste byproduct of the alumina recovery process, is a serious ecological and environmental issue. With ~150 million tons/year of RM being generated globally, nearly 4.6 billion tons of RM are presently stored in vast waste reserves. RM can be a valuable resource of metals, minor elements, and rare earth elements. The suitability of RM as a low-grade iron resource was assessed in this study. The utilization of RM as a material resource in several commercial, industrial operations was briefly reviewed. Key features of iron recovery techniques, such as magnetic separation, carbothermal reduction, smelting reduction, acid leaching, and hydrothermal techniques were presented. RMs from different parts of the globe including India, China, Greece, Italy, France, and Russia were examined for their iron recovery potential. Data on RM composition, iron recovery, techniques, and yields was presented. The composition range of RMs examined were: Fe2O3: 28.3–63.2 wt.%; Al2O3: 6.9–26.53 wt.%; SiO2: 2.3–22.0 wt.%; Na2O: 0.27–13.44 wt.%; CaO: 0.26–23.8 wt.%; Al2O3/SiO2: 0.3–4.6. Even with a high alumina content and high Al2O3/SiO2 ratios, it was possible to recover iron in all cases, showing the significant potential of RM as a secondary resource of low-grade iron.

Deposits in Gas-fired Rotary Kiln for Limonite Magnetization-Reduction Roasting: Characteristics and Formation Mechanism

The formation mechanism of deposits in commercial gas-fired magnetization-reduction roasting rotary kiln was studied. The deposits ring adhered on the kiln wall based on the bonding of low melting point eutectic liquid phase, and the deposit adhered on the air duct head by impact deposition. The chemical composition and microstructure of the deposits sampled at different locations varied slightly. Besides a small amount of quartz and limonite, main phases in the deposits are fayalite, glass phase and magnetite. The formation of the deposits can be attributed to the derivation of low melting point eutectic of fine limonite and coal ash, and the solid state reaction between them. Coal ash, originated from the reduction coal, combining together with fine limonite particles, results in the accumulation of deposits on the kiln wall and air duct. Fayalite, the binder phase, was a key factor for deposit formation. The residual carbon in limonite may cause an over-reduction of limonite and produce FeO. Amid the roasting process, SiO2, originated from limonite and coal ash, may combine with FeO and reduce the liquefaction temperature, therewith liquid phase generates at high temperature zone, which can significantly promote the growth of deposits.