Direct reduction features of iron ore by lignocellulosic biomass and its components

Direct Reduction (DR) of natural hematite fines, 90–200 µm Khumani iron ore (IOK), by lignocellulosic biomass, Beechwood (BW), its torrefied form (TBW), and its components, lignin (LIG), hemicellulose (HEM) and cellulose (CEL), has been carried out in a thermogravimetric apparatus coupled with evolved gas analysis at different weight ratios. The qualitative analysis of materials has been carried out via X-Ray Fluorescence. The microstructural variations and the reduction degree of IOK have been determined by means of X-Ray Diffraction. It has been highlighted that BW, and its single components can effectively reduce IOK under well selected conditions, however the reducing power scales in the order LIG > TBW > CEL > BW > HEM. Biomass pyrolysis is minimally affected by the IOK presence up to 600 °C. At higher temperatures, the biochar, derived from the biomass pyrolysis one-pot, acts as a reducing agent, leading to the progressive IOK reduction: Fe2O3 → Fe3O4 → FeO → Fe. Simultaneously, the fixed carbon is oxidized, releasing CO2 and primarily CO. The IOK reduction at high temperature is governed by the amount of the fixed carbon which acts as the limiting reagent; therefore, the complete DR has been achieved with sub-stoichiometric oxygen, (oxygen to carbon ratio < 1)