This study investigates the non-isothermal reduction of iron ore fines with two different carbon-bearing materials using the thermogravimetric technique. The iron ore fines/carbon composites were heated from room temperature up to 1100 °C with different heating rates (5, 10, 15, and 20 °C/min) under an argon atmosphere. The effect of heating rates and carbon sources on the reduction rate was intensively investigated. Reflected light and scanning electron microscopes were used to examine the morphological structure of the reduced composite. The results showed that the heating rates affected the reduction extent and the reduction rate. Under the same heating rate, the rates of reduction were relatively higher by using charcoal than coal. The reduction behavior of iron ore-coal was proceeded step wisely as follows: Fe2O3 → Fe3O4 → FeO → Fe. The reduction of iron ore/charcoal was proceeded from Fe2O3 to FeO and finally from FeO to metallic iron. The reduction kinetics was deduced by applying two different methods (model-free and model-fitting). The calculated activation energies of Fe2O3/charcoal and of Fe2O3/coal are 40.50–190.12 kJ/mole and 55.02–220.12 kJ/mole, respectively. These indicated that the reduction is controlled by gas diffusion at the initial stages and by nucleation reaction at the final stages.
The swelling ratio of a packed coal bed in a coal liquefaction process derived recycle solvent (REC) and pure tetralin (THN) at elevated temperature and pressure is obtained by a so‐called linear variable differential transformer (LVDT) deformation transducer apparatus. Effects of heating rate and coal rank on the swelling behavior are investigated. A kinetic model based on a pseudopolymolecular reaction is used to model the swelling data up to the maximum swelling ratio. With the increase of the temperature, the thermal motion of solvent molecule and coal macromolecules is enhanced, and the interactions increase between coal macromolecules and solvent molecule. As the temperature is further increased, the swelling ratio of the packed coal bed reduces for the softening and decomposition of coal. For faster heating rates, the maximum swelling ratio shifts to higher temperature and the apparent activation energy and pre‐exponential factor slightly increase with the increase of heating rates. A comparison of coal rank illustrates that the maximum swelling ratio of bituminous coal in REC and THN is more and shows at higher temperature than lignite. The apparent activation energy for coals swelling in REC and THN at elevated temperature and pressure is between 20 and 55 kJ/mol. © 2016 Curtin University of Technology and John Wiley & Sons, Ltd.
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