This work was devoted to the kinetics studies of the oxidation of divalent iron in liquid FeOCaO-SiO 2 slags to the trivalent state. The experiments were carried out using a thermogravimetric technique (TGA) in the temperature range of 1623 K to 1773 K (1350°C to 1500°C) in an oxidizing atmosphere. The reaction products after oxidation were analyzed by X-ray diffraction and optical and scanning electron microscopy. The results obtained show that during the first 10 to 15 minutes of oxidation, 70 to 90 pct of the Fe 2+ in the slag was oxidized. Kinetic analysis of the TGA results indicates that the oxidation process may consist of three distinct steps, viz an initial incubation period, followed by a chemical-reaction-controlled stage, and later, a diffusion-control stage. Appropriate mathematical relationships were set up for the first two consecutive steps. After combining these equations suitably as the mechanism of oxidation shifts from one form to another, the experimental results for the first two parts could be reproduced. A linear correlation was found between the thermodynamic activity of FeO in the slag and the degree of oxidation.

The current work investigates dynamic phenomena at the microstructural level during iron and manganese recovery from the liquid FeO-CaO-SiO 2 -MnO slags using an oxidation method. A hot-stage-equipped confocal scanning laser microscope (CSLM) was used to analyze the kinetic behavior of crystallization in synthetic slags. Based on observed precipitations on cooling in the 1273 K (1000°C) to 1873 K (1600°C) temperature range, a timetemperature-transformation (TTT) diagram has been created. The crystallization studies were conducted in air.

The oxidation of FeO in 30 wt pct FeO-35 wt pct CaO-35 wt pct SiO 2 slag was investigated as part of a wider study on the recovery of Fe units through magnetic separation. A confocal scanning laser microscopy (CSLM) technique was used to visualize the oxidation of FeO in the liquid slag. The formation event was observed in situ under the CSLM and the onset of precipitation on a surface of the slag liquid was recorded at various temperatures in an oxidizing atmosphere. A Time-Temperature-Transformation (TTT) diagram was constructed based on the CSLM results. Samples obtained from the CSLM heating chamber were analyzed by a scanning electron microscope (SEM) equipped with an energy-dispersive spectrometer (EDS).

X-ray tomography was applied to the investigation of the structure of sinter mixture granules. Different components such as ore, concentrate, coke breeze and limestone were identified and their sizes and spatial distribution estimated. Classification of the granule structure by the thickness of the adhering fines layer in a proportion to the whole granule radius has been estimated. Excessive amount of fines (concentrate) in a mixture leads to the increasing presence of granules with an adhering fines layer thicker than a half of the granule radius. Abnormal structures of granules have been observed in some cases such as microgranules embedded in the adhering layer of bigger granules, granules formed as the result of two or more granules coalescence or granules formed without a nucleus particle with a structure similar to pellets.

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