Iron Recovery from Bauxite Tailings Red Mud by Thermal Reduction with Blast Furnace Sludge

• Main Authors: Davide Mombelli, Silvia Barella, Andrea Gruttadauria, Carlo Mapelli
• Format: Article
• Language: English
• Published: MDPI AG 2019-11-01
• Series: Applied Sciences
• Subjects: red mud; blast furnace sludge; reduction; environmental impact; circular economy; recycling
• Online Access: https://www.mdpi.com/2076-3417/9/22/4902

More than 100 million tons of red mud were produced annually in the world over the short time range from 2011 to 2018. Red mud represents one of the metallurgical by-products more difficult to dispose of due to the high alkalinity (pH 10−13) and storage techniques issues. Up to now, economically viable commercial processes for the recovery and the reuse of these waste were not available. Due to the high content of iron oxide (30−60% wt.) red mud ranks as a potential raw material for the production of iron through a direct route. In this work, a novel process at the laboratory scale to produce iron sponge (≤ 1300 °C) or cast iron (> 1300 °C) using blast furnace sludge as a reducing agent is presented. Red mud-reducing agent mixes were reduced in a muffle furnace at 1200, 1300, and 1500 °C for 15 min. Pure graphite and blast furnace sludges were used as reducing agents with different equivalent carbon concentrations. The results confirmed the blast furnace sludge as a suitable reducing agent to recover the iron fraction contained in the red mud. For all the conditions tested, the metallization degree was higher than 70%, and the best condition to reduce red mud through blast furnace sludge was identified at 1:1 red mud/blast furnace (B.F.) sludges equal to 0.85 C/Fe₂O₃.