(521b) Red Mud As a Catalyst and Oxygen Carrier in Biomass Gasification: A Route to Recover Iron from Bauxite Residue

Over 150 million tonnes of red mud, a harmful residue from alumina production, are generated per year globally. The main component of red mud is hematite, hence the name red mud. This work aims to provide an experimental proof-of-concept of using red mud as an oxygen carrier and catalyst in biomass gasification and evaluate the suitability of this process as a reduction roasting methodology for iron recovery. A 5 g sample was reacted with methane in a bench-scale packed bed reactor. The reactor temperature was raised to 800 °C and then held isothermal for 30 min. Exhaust gases were analyzed using a gas chromatograph. The attached figure shows the XRD diffraction pattern of red mud samples before and after the methane experiment. The iron content in the red mud was reduced from hematite (Fe₂O₃; 31%) and perovskite (CaFeO₃, 7%) to metallic iron (Fe; 12.1%) and cohenite (Fe₃C; 45.5%). The formation of CO was verified through GC analysis, which indicates that Red mud can work as an oxygen carrier. We plan to perform three experiments using: a) biomass; b) a mixture of biomass and red mud; and c) biomass and red mud separated by glass wool. Experimental and analysis conditions will be the same as in the methane experiment, but with a water vapor-saturated nitrogen stream. Experiment "a" will provide a blank parameter for the evaluation of catalyzed experiments. Experiment "b" will test the hypothesis of the applicability of red mud as a catalyst/oxygen carrier for biomass gasification. Experiment "c" will produce evidence concerning the cracking catalytical activity of red mud.

This work is part of the Abtomat project (2021-05201) funded by Vinnova via the ERA-NET Cofund on Raw Materials (ERA-MIN3) program. The authors thank the project consortium partners for the discussions. We also thank ETI Aluminyum for the samples.