Interactions among magnetite oxidation, calcination of carbonate minerals and melt formation in iron ore pellets

Firth, Andrew Robert

doi:10.1179/174328507x163896

Cited by 5 publications

(3 citation statements)

References 2 publications

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“…At temperatures above 1150 °C, the eutectic slag becomes widespread between the magnetite grains, allowing significant sintering to occur (Figure 5). This is different to the outer hematite zone of the pellet where significant molten slag formation does not occur until around 1200 °C (10) . Note that Figure 5 exaggerates the amount of slag formed due to the longer time at temperature and higher gangue composition compared to real iron ore pellets.…”

Section: Results For Compacts With Reduced Oxygenmentioning

confidence: 67%

“…Rapid quenching of the samples was performed using a high flowrate of nitrogen gas. The test method used here was originally developed by Firth (10) for the evaluation of firing profiles for pellets produced from Australian magnetite concentrates. Single green balls of a suitable size, about 12.5 mm in diameter, were placed in a nickel foil crucible before being place in the furnace with an R type thermocouple (platinum -platinum-10% rhodium) used to measure the surface temperature of the pellet.…”

Section: Methodsmentioning

confidence: 99%

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Phase Relations in the Magnetite Core of Iron Ore Pellets

Firth,

Garden,

Douglas

2007

ABM Proceedings

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During the induration of pellets produced from magnetite concentrates, oxygen access to the core is restricted while slag formation is occurring. This situation is analogous to what happens in the core of pellets produced from hematite concentrates with added carbon, where significant amounts of secondary magnetite are formed from hematite being reduced. Individual green balls and compacts of ground magnetite ore, limestone flux, silica and carbon were fired at precisely controlled temperatures to determine what slag phases formed at that temperature, especially in the core. In some cases, more silica and lime was added than in real pellets to produce larger quantities of slag that were easier to characterise. Optical and scanning electron microscopy showed that the lack of oxygen in the core of the pellets results in the onset of calcium silicate slag formation at lower temperatures, around 1100 °C. The initial slag may not be fully molten, however, as the slag phase does not cover the particles until the temperature exceeds 1250 °C. The quicker onset of slag formation in the core often results in greater sintering than in the shell of the pellet, causing the core to pull away. As a result, low compressive strengths are obtained.

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Section: Results For Compacts With Reduced Oxygenmentioning

confidence: 67%

Section: Methodsmentioning

confidence: 99%

Phase Relations in the Magnetite Core of Iron Ore Pellets

Firth,

Garden,

Douglas

2007

ABM Proceedings

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“…Currently, many metallurgists have carried out a lot of research on the preparation of fluxed pellets [5]. Firth et al [6][7][8] used low-silica magnetite (65.7% Fe (total), 2.3% SiO 2 ) with limestone and dolomite to prepare fluxed pellets with basicity (CaO/SiO 2 ) of 1.0; They found that while the magnetite is being oxidized to haematite, carbonate fluxes are being calcined, leading to the formation of complex oxides. Calcination of fluxes and the formation of calcium and magnesium ferrites and silicates during the preheat stage can influence the magnetite oxidation process.…”

Section: Introductionmentioning

confidence: 99%

Phase transition mechanism of high-silica fluxed pellets during consolidation

Zhang

Wang

et al. 2022

Ironmaking & Steelmaking

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An in-depth study of the consolidation behaviour of high-silica fluxed pellets will help promote the development of a high-proportion pellet smelting process suitable for China's resource structure. Lime, slaked lime, and limestone were used as calcium-containing additives to prepare high-silica fluxed pellets, and the suitable calcium-containing additives were lime and limestone. Compared with acid pellets, the suitable preheating temperature of high-silica fluxed pellets is higher (1100°C). The phase transformation during preheating consists mainly of the thermal decomposition of CaCO 3 and Ca (OH) 2 and the reaction between the solid phases.The roasting temperature of highsilica fluxed pellets should be controlled within a small range (1250°C-1280°C). The phase transition during the roasting of mainly lies in the generation and migration of the liquid phase. The Fe 2 O 3 consolidation, the pore distribution law, and the liquid phase formation jointly determine the consolidation properties of the pellet.

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