Iron Ore Reduction by Biomass Volatiles

Abstract

The use of biomass in different routes of ironmaking has been recently investigated. Although the volatile matter is the major constituent of the biomass, its contribution as reducing agent has not been explored in detail. This work aimed to investigate the reduction of iron ore by biomass volatiles and elucidate the steps involved, searching for optimization of its use in the ironmaking industry. Experiments with biomass and iron ore packed beds placed separately were carried out in the interval between 200 and 1000 °C in an infrared furnace. Iron ore reduction was observed at low temperatures (< 800 °C) and increased up to 1000 °C, where wustite, metallic iron and cementite were detected by XRD. Carbon deposition at low temperatures and carbothermic reduction at high temperatures were identified through carbon analysis and thermal profile measures. At low temperature the reduction occurred mainly by the non-condensable gases (CO, H2) from biomass pyrolysis and tar cracking reactions, while from 800 °C the reduction advanced by carbon deposited on the iron ore. The activation energy for the carbothermic reduction indicated the carbon gasification as the reaction-limiting step. The deposited carbon proved to be more reactive than other carbon sources commonly used in the ironmaking.