A New Strategy for Collaborative Utilization of Red Mud and Coal Fly Ash via Vacuum Reduction Technology

摘要

The clean recovery of red mud (RM) and coal fly ash (CFA) has drawn widespread attentions owing to the increasing awareness of environmental protection. In this study, a new strategy for recycling RM and CFA simultaneously by extracting valuable metallic elements from them was proposed. The process is mainly composed of two stages, e.g., vacuum carbothermal reduction and magnetic separation. The effects of RM/CFA ratio, duration, and temperature on the mineralogical evolution of RM and CFA during the vacuum reduction were investigated thoroughly. The results show that the Fe-Si alloys can be prepared effectively by the vacuum reduction of RM and CFA because the hematite (Fe2O3) in RM can react with the mullite (Al6Si2O13) in CFA to form Fe-Si alloys at a low temperature. Additionally, the produced Fe-Si alloys and the other valuable components can be separated through the magnetic separation, because of the strong magnetic property of the Fe-Si alloys. After separation, the magnetic portion was mainly composed of Fe5Si3 and FeSi phases, while the non-magnetic portion consisted of 64.04 wt% Al2O3, 7.49 wt% SiO2, and 10.35 wt% TiO2. The alumina/silica mass ratio (A/S) in the non-magnetic product achieved 8.55, which is similar to that of the high-quality bauxite ores and can be a raw material to produce alumina and enrich titanium by the Bayer process. This strategy takes full advantages of the valuable metals in the RM and CFA, which shows a good prospect for industrial application. [GRAPHICS] .