Kinetics and mechanisms of direct reduction of iron ore-biomass composite pellets with hydrogen gas

摘要

Direct reduction of iron ore pellets (DRI) with and without biomass was studied using hydrogen as the reducing agent. The influences of temperature and time on the reduction rate of pellets were investigated. X-ray diffraction (XRD), scanning electron microscopy (SEM) and BET (Bet specific surface area) tests were adopted to interpret the mechanism of Fe2O3 reduction with H-2, as well as explore the role of biomass in pellets during the reduction process. Results show that the biomass not only improve the reduction extent of the pellets, but also increase the reduction velocity index (RVI) of the pellets by 1.12%/min. The BET test indicates that the existence of biomass can create porosity in pellets by dehydration and combustion/pyrolysis, which increases the contact area between iron oxide and reducing gas during reduction process, and decreases the apparent activation energy of pellets from 122 kJ mol(-1) (without biomass) to 111 kJ moll (with biomass). For the DRI process, the crucial reduction step FeO -> Fe is controlled by the intrinsic interfacial chemical reaction. Copyright (C) 2015, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.