Demonstration of Scaled-Production of Rare Earth Oxides and Critical Materials from Coal-Based Sources Using Innovative, Low Cost Process Technologies and Circuits

A projected exponential increase in the production of electric vehicles and high-end advanced technologies including those used in the defense industry is expected to require nearly double the amount of rare earth elements (REEs) and critical elements currently available worldwide. The difficulties associated with this issue is compounded by the worldwide imbalance in supply with China being the primary source for REEs and other critical materials. Due to market conditions, ideal sources are mining operations that currently produce a primary product and a waste material containing elevated concentrations of REEs that can be economically recovered. Research sponsored by the U.S. Department of Energy (U.S. DOE) has found that the current waste generated by coal mining and processing contains the amount of REEs needed to meet the annual U.S. demand. To assess the technical and economic potential of extracting REEs from coal waste, a ¼-ton/hr mobile pilot plant was designed, constructed and tested as part of an on-going project funded by U.S. DOE. Although the pilot plant was successful in recovering REEs and producing rare earth oxide (REO) mixes having a purity level greater than 90%, several economic barriers were realized that require more detailed evaluations and a modification of the process circuitry. Most importantly, a reduction in the chemical costs per kilogram of REO recovered is needed for the process to be economically viable for a typical coal source. It is, therefore, proposed to extend the activities of the existing REE pilot plant to integrate and test new technologies and circuits that will significantly reduce the cost of producing REO mixes, cobalt and manganese at purity levels significantly greater than 2% by weight. Concentrate production will be increased from a current rate of 10 – 100 grams/day to around 200 grams/day. To significantly reduce the primary cost of producing the concentrates, naturally occurring coal pyrite will be recovered and used in bioreactors to produce the acid needed for leaching. Optimization of the conditions will be conducted in laboratory and pilot plant test programs. High-temperature pretreatment of the feed to the leach reactor will be optimized with chemical additives to significantly improve REE recovery and, in the case of magnetite addition, provide the potential for acid generation to aid in acid cost reduction efforts. Selective precipitation will be added and optimized as a means of elevating the REE concentration in the pregnant liquid solution (PLS) prior to the final concentration steps. Calcite will be recovered from coal to be used for increasing solution pH values. The research program will be managed and conducted by a team of researchers from the University of Kentucky, University of Utah and Virginia Tech. Alliance Coal will host and provide operational support for the pilot plant as well as the necessary amount of a qualified feedstock. Kentucky River Properties will be a team partner and will work with the project team to collect and transport several tons of the second qualified feedstock to the pilot plant location. Mineral Separation Technologies will provide a dual x-ray transmission sorter to provide the initial concentration of REEs and critical materials.