Stepwise Reduction of CaO and/or MgO Doped-Fe_2O_3 Compacts to Magnetite Then Subsequently to Iron at 1173-1473 K

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概要

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• Compacts of pure Fe2O3 and Fe2O3-doped with either of 1.0 % CaO and/or 1.0 % MgO, sintered at 1473 K for 20 h, were isothermally reduced at 1173-1473 K with 10%CO-90%CO2 to magnetite then to metallic iron with purified CO. The oxygen weight-loss resulted from Fe2O3-Fe3O4 or Fe3O4-Fe reduction steps was continuously recorded as a function of time. Chemical and X-ray analyses, microscope examination and pore size analyzer were used to characterize the fired and reduced compacts. The influence of CaO and/or MgO on the reduction behaviour of Fe2O3 and Fe3O4 was intensively studied. The reduction mechanisms predicted from both of apparent activation energy values and heterogeneous gas-solid mathematical models were correlated with the microstructures of partially reduced samples. The results obtained showed that the doping of these fluxing oxides promoted the reduction of Fe2O3 at 1173-1473 K. The reduction of pure and doped Fe2O3 compacts is controlled by gaseous diffusion at early stages and by interfacial chemical reaction at later stages. In Fe3O4-Fe reduction step, the doping of CaO and/or MgO enhanced the reduction at early stages which is temperature and compact composition dependent. With progress in reduction, the presence of MgO retarded the reduction of Fe3O4 at ≤1273 K resulting a slowing down in the rate at latter stages. This was attributed to formation of entrapped lower oxide relics which hindered gaseous diffusion. At early stages, the reduction of pure and doped Fe3O4 compacts is controlled by mixed control reaction mechanism. At latter stages, interfacial chemical reaction is the rate determining step for pure and CaO-containing samples, whereas solid-state diffusion is the rate controlling step for MgO-doped compacts.

• 社団法人 日本鉄鋼協会の論文
• 1997-09-15

著者

• EL-GEASSY A.

  Central Metallurgical Res. & Devlopment Inst. (CMRDI)

• El‐geassy A

  Central Metallurgical Res. & Devlopment Inst. (cmrdi)

関連論文

• Reduction Behaviour of Iron Ore Fluxed Pellets under Load at 1023-1273K
• Effect of Nickel Oxide Doping on the Kinetics and Mechanism of Iron Oxide Reduction
• Effect of Reducing Gas on the Volume Change during Reduction of Iron Oxide Compacts
• Stepwise Reduction of CaO and/or MgO Doped-Fe_2O_3 Compacts to Magnetite Then Subsequently to Iron at 1173-1473 K
• Gaseous Reduction of MgO-doped Fe_2O_3 Compacts with Carbon-monoxide at 1173-1473K
• Reduction of CaO and/or MgO-doped Fe_2O_3 Compacts with Carbon-monoxide at 1173-1473K

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