October_AMP_Digital

A D V A N C E D M A T E R I A L S & P R O C E S S E S | O C T O B E R 2 0 2 0 2 4 I n the United States, coal is a vast nat- ural resource that powered the Indus- trial Revolution and has dominated the electric power industry for decades. In 2018, the U.S. Energy Information Ad- ministration (EIA) estimated there are more than 253 billion short tons of do- mestic coal reserves—enough to ener- gize the country for hundreds of years. The potential for coal to impact and rev- olutionize U.S. industries goes beyond its heating value. For example, the use of coal combustion by-products has seen tremendous growth in the production of construction materials such as concrete and wallboard. Continuing to unlock coal’s unique characteristics and future industrial ca- pability has been an objective of the U.S. Department of Energy (DOE)/Na- tional Energy Technology Laboratory (NETL) for many years. The initiation of DOE/NETL’s Feasibility of Recover- ing Rare Earth Elements program in 2014 further exemplifies the objective of unleashing coal’s full potential with a focused effort to produce salable rare earth elements (REEs) from domestic coal and coal-based resources. The importance of REEs cannot be overstated. With hundreds of end uses and applications in clean energy pro- duction, oil refining, electronics, batter- ies for electric vehicles, phosphors for lighting, and defense technologies, rare earths are critical to the stability and growth of modern society. However, the U.S. is heavily reliant on imports to supply REEs and compounds as well as intermediate and end products contain- ing rare earths such as permanent mag- nets, motors, and turbines. This reliance on imports for REEs causes supply and price risk concerns. One possible solu- tion is turning to abundant U.S. coal resources for a domestic, economical, reliable, and environmentally benign source of REEs. With an average concen- tration of 62 parts per million (ppm) of REEs in U.S. coal, there were more than 45,000 tons of REEs contained in coal mined in the U.S. in 2018—more than quadruple U.S. REE consumption [1] . Al- though this is a remarkable quantity of REEs, the challenge is developing eco- nomical separation technologies for producing REEs from coal and coal- based resources. FIELD SAMPLING To extract REEs from any source, materials characterization information must be initially obtained, which in- cludes determining the concentration or grade of REEs in the source material, as well as the chemical phase or min- eral in which the REEs are contained. With expansive coal reserves and mil- lions to billions of tons of coal refuse, coal ash, and acid mine drainage (AMD) water and sludge scattered across the country [2-4] , determining the best mate- rials and samples, locations, and coal seams, as well as materials in terms of the contained REE concentration, is an extensive effort. As part of NETL’s REE program portfolio, projects are required to pro- vide elemental characterization infor- mation for materials identified during prospecting efforts, as well as during processing where REEs are extracted through physical beneficiation, sepa- rated though chemical processing, and recovered as either mixed or individu- ally separated rare earth oxides (REOs). This information is uploaded to NETL’s Energy Data eXchange (EDX) website [4] for public use. In addition to these data, published REE datasets such as the U.S. Geological Survey (USGS) Coal Quali- ty (COALQUAL) database [5,6] and jour- nal publications are viewed as valuable LOCATING AND EXTRACTING RARE EARTH ELEMENTS FROM DOMESTIC COAL-BASED RESOURCES Even with the recent downturn in coal production, the amount of coal being mined and utilized in the U.S. contains more than four times the current domestic consumption of rare earth elements. Elliot Roth, KeyLogic Systems LLC, Morgantown, West Virginia Mary Anne Alvin, National Energy Technology Laboratory, Pittsburgh