Production of Critical Minerals from Coal Ash

Coal byproducts are a potential source of rare earth elements (REEs). New technologies to recover REEs from these feedstocks will enable utilization of coal combustion waste in environmentally benign ways to produce strategically important materials. Our goal was to develop and demonstrate a pilot plant that recovers REEs from coal ash via economical and environmentally-friendly processes. The team collected, processed, and concentrated REEs from coal ash deposits located across the Southeastern U.S. We constructed and operated a sub-scale (0.5 kg/day) micropilot facility to demonstrate the key physical and chemical processing operations, predict yields, and troubleshoot process bottlenecks. The project team designed, constructed and operated two decoupled pilot plant operations: (1) an operational pilot plant for physical separation processes with a capacity of 0.4 metric tons per day (tpd) where we optimized processes to generate selected ash fractions as the feedstock for chemical processing as well as byproducts such as cenospheres, magnetic ash and secondary fuel carbon, and (2) an operational pilot plant for chemical ash processing with a capacity of 0.5 tpd that developed optimized processes for the production of REEs and beneficiated ash as valuable byproduct suitable for cement applications. The team achieved REE purities in excess of 90 wt.% (oxide basis) and generated >100 g of REE concentrate material. This work reports on a potential new domestic resource for REEs.