Preparation of Reduced Iron Powder and Cement Raw Material from Red Mud Using Reduction Roasting with CaO

Abstract

Reduction roasting‒magnetic separation was adopted to extract iron in red mud containing 47.45% Fe and 11.58% Al₂O₃. The process mineralogy and phase transformation of red mud during reduction roasting with CaO were studied using advanced mineral identification and characterization system, X-ray diffraction, scanning electron microscope, and energy-dispersive spectrometer. Results show that the main Fe-bearing minerals in red mud are hematite and alumogeothite, with corresponding contents of 47.99% and 37.81%, respectively. After reduction roasting with CaO, red mud is converted into metallic iron and Ca–Al compounds, and the iron grain size increases with roasting temperature. After roasting at 1175 °C for 60 min, the iron grain size reaches 18.85 μm. Under the conditions of grinding size of − 44 μm of 86.57%, and magnetic intensity of 1000 Gs, a concentrate with Fe grade of 90.14% and Fe recovery of 85.68% is obtained. Meanwhile, there are 40.01% of CaO and 23.96% of Al₂O₃ in magnetic tailing, which can be used as cement raw materials. This study lays the foundation for the resource utilization of red mud.

Graphical Abstract