The correlation between structural and reduction kinetics of carbon from agricultural waste with hematite

Abstract

Char conversion by pyrolysis is a promising technique for the production of renewable carbon source. In this study, char generated from agricultural waste (i.e. palm shell) was studied as reductant instead of fossil fuels. The palm shell char was prepared by chemical activation using orthophosphoric acid and pyrolysis under an inert atmosphere at 723 K. The reduction experiment was conducted to understand the reduction of iron oxide with palm shell char where the associated reaction kinetics was elucidated. The reduction conditions were kept constant for 30 min, C/O ratio was 0.6 and particle size <63 μm. The reduction experiments were conducted in the temperature range 1523−1823 K in a horizontal tube furnace under argon gas. Scanning electron microscope (SEM) was employed to determine the structure of reduced samples. The results showed that the reduction temperature was responsible for structural evolutions during reduction. The iron oxide was completely reduced to metallic iron with palm shell char at 1823 K and this temperature was considered optimum for the desired conversion. X-ray diffraction (XRD) and energy dispersive X-ray spectroscopy (EDX) confirmed the formation of metallic iron after the reduction reaction. The activation energy of hematite reduction by palm shell char was 117 kJ mol−1 and this indicated the reduction occurs in a rapid manner. The palm shell char is highly reactive as reductant and this correlated well with the reduction kinetics at high temperature. This study provided insight on the ideal approach of agricultural waste as a renewable carbon reductant for steelmaking applications. Keywords: Agricultural waste, Palm shell char, Reduction kinetics, Sustainable ironmaking