Reduction Behavior and Kinetics of Iron Ore–Charcoal Composite Pellets for Sustainable Ironmaking

Abstract

Applications of carbon–neutral biomasses and derived charcoals have potential to reduce GHG emissions in the steel industry. The reduction behavior and kinetics of iron ore coal composite pellets for ironmaking have been studied extensively by several researchers. However, fast-growing and high-carbon yielding hardwood biomasses such as Acacia (W1), Albizia (W2), and Leucaena (W3) have not been explored as reductants in ironmaking. Charcoals from the same biomasses were chosen in the present study to make composite pellets with iron ore. Effect of C/O ratio, carbonization temperature, reduction temperature, reduction time, and the charcoal types on the reduction behavior of iron ore charcoal composite pellets were studied. Reduction kinetics was studied using three popular models. Results indicate that the optimum C/O ratio and carbonization temperature are 1.5 and 800 °C, respectively. Degree of reduction or %Reduction (%R) of composite pellets was found higher with W1 (82 pct) and W3 (83 pct) charcoals than with W2 (70 pct). %Metallization (%M), X-ray diffraction, and SEM images confirm the trend in %R. The gas diffusion model fits best to the experimental data. Activation energies for reduction of composite pellets with W1, W2, and W3 charcoals were found to be 191, 213, and 170 kJ/mol, respectively. Charcoal being CO2 neutral and more reactive than coal is a better alternative to coal in ironmaking. W1 and W3 turned out to be better reductants than W2 charcoal among the selected biomasses. © 2023, The Minerals, Metals & Materials Society and ASM International.