Multistep Reduction Kinetics of Fine Iron Ore with Carbon Monoxide in a Micro Fluidized Bed Reaction Analyzer
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GASEOUS reduction of iron ores in fluidized beds plays an important role in the fields of metallurgical industry and chemical engineering, such as direct reduction process and chemical looping combustion (CLC) which are both under development. Direct reduced iron can be produced from fine iron ores by gaseous reduction in a fluidized bed reactor, which contributes to the establishment of an alternative and simplified ironmaking process by eliminating the procedures of sintering/agglomeration and coke making that cause large material/energy consumptions and environmental problems.[1,2] Chemical looping combustion[3–5] has emerged as one of the promising technologies for the efficient fossil fuel conversion with inherent CO2 capture in dual fluidized bed systems. Iron ores are believed to be one of the potential oxygen carriers for commercial and industrial chemical looping combustion applications with respect to the advantages such as environmentally friendly, relatively cheap, and readily HONGSHENG CHEN, ZHONG ZHENG, and WENZHOU YU are with the College of Materials Science and Engineering, Chongqing University, No.174, Shazheng Street, Shapingba District, Chongqing, 400044, P.R. China. Contact e-mails: [email protected] ZHIWEI CHEN is with the Fluidization Research Center, Department of Chemical and Biological Engineering, University of British Columbia, Vancouver V6T 1Z3, Canada. Contact e-mail: [email protected] JUNRONG YUE is with the State Key Laboratory of Multi-phase Complex System, Institute of Process Engineering, Beijing 100090, P.R. China. Manuscript submitted February 29, 2016. METALLURGICAL AND MATERIALS TRANSACTIONS B
available.[6–9] However, the reduction process of iron oxides into iron is heterogeneous and complex as several elementary reactions take place simultaneously. A better understanding of the reduction kinetics of iron oxides in a fluidized bed promotes the development of relevant industrial processes. In general, the reduction route of iron oxides is considered to be a chain of single-step reactions as Fe2O3 fi Fe3O4 fi FeO fi Fe when temperature is higher than 843 K (570 C).[10,11] Nevertheless, other reduction routes, e.g., Fe2 O3 ! Fe3 O4 ! Fe and Fe2 O3 ! FeO ! Fe were also reported.[12] Wu¨stite is considered to be stoichiometric in this paper. A survey of the literature related to the reduction kinetics of iron oxides indicates that a number of investigations have contributed to the multistep characteristics of the reduction process. Sun et al.[13] studied the reduction kinetics of oolitic iron ore by dividing the reduction rate curves into initial, intermediate, and final stages, the apparent activation energies of the three stages were also evaluated. Weiss et al.[14] investigated the reduction of hematite fines in an elevated pressure fluidized bed using H2-rich reducing gases, the kinetic parameters of Fe2O3 fi Fe3O4, Fe3O4 fi FeO, and FeO fi Fe were obtained. As well known, the concentration of hematite decreases steadily with time during the reduction process, the magnetite that formed by he
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