Enhancing low-carbon iron and steel production with torrefied biomass

This study investigated the potential use of as-received and torrefied biomass of the genus Pine, in the form of wood bark (CC), chips (CV) and pelletized wood (PP), as a substitute for metallurgical coke, to reduce the high generation of CO2 in blast furnaces. The thermal treatment at 290 °C and residence time of 30 min yielded the highest reactivity for CV and PP biomasses with CO2, while for CC biomass the optimal experimental conditions were 250 °C and 60 min. The ore reduction was performed by thermogravimetry using a mixture of iron oxide and biomass (as received or torrefied) in the massic proportion of 1:1. The iron oxide reduction was evaluated by comparing the theoretical and experimental reduction curves, DTG and XPS results. In addition, a microscope was used to visualize the coloration of the mixtures before and after reduction, as an indicative for the iron oxide reduction characterized by the darkening of the samples before and after the thermogravimetric tests. The results indicate that the mixtures containing torrefied biomass presented greater improvements than the mixtures with as-received biomass, indicating the importance of torrefaction in this application. Furthermore, from the TGA, DTG and thermodynamic analysis data, it was observed that the gradual reduction of Fe2O3→Fe3O4 →FeO→Fe must have occurred from 350 °C to 860–1000 °C. Finally, the XPS analysis showed the presence of Fe and its oxides in the torrefied biomass mixtures that underwent reduction, indicating a partial reduction of the iron ore. ●As-Received and torrefied biomass was investigated as a substitute for metallurgical coke in blast furnaces.●The iron ore reduction with biomass was carried out using thermogravimetric analysis.●The iron ore reduction was evaluated by comparing the theoretical and experimental reduction curves, DTG and XPS.●The use of torrefied biomass provided greater iron oxide reduction than fresh biomass.