Can rare earth elements (REEs) be economically recovered from coal and coal byproducts? Battelle researchers are conducting studies to find out. The project, “Recovery of Rare Earth Elements from Coal with a Closed Loop Leaching Process,”funded by the U.S. Department of Energy (DOE) and the Ohio Coal Development Office (OCDO), will develop and test Battelle’s patented closed-loop acid digestion process for recovery of REEs from Ohio-based Middle Kittanning coal and post-combustion coal ash.
REEs are a set of 17 elements found in the Earth’s crust that have unique chemical properties that make them highly valuable for many technology applications. REEs such as cerium, lanthanum and scandium have become essential components of technologies used in applications spanning electronics, computer and communication systems, transportation, health care and national defense. While REEs are not necessarily rare in nature, they are often difficult to extract. Over the last few decades, the number of applications for REEs has exploded, driving up costs and straining global supply chains. As a result, interest is growing in economically feasible approaches for REE recovery from alternative sources.
In response to this need, the DOE’s National Energy Technology Laboratory (NETL) has selected 10 projects to receive funding for research into REE recovery. The selected research projects will focus on the development of cost-effective and environmentally benign approaches from domestic coal and coal byproducts.
Battelle, with support from its partners, is conducting research to validate the economic viability of Battelle’s patented closed-loop Acid Digestion Process (ADP) for recovering REEs from coal ash. Researchers will select coal sources with the potential to provide REE concentrations above 300 parts per million by weight, collect characterization data for coal ash samples generated via three different methods, and perform a techno-economic analysis for the use of the ADP in REE extraction. Three sources of coal ash will be targeted for evaluation in this project:
- Coal ash from power generation stations, to include fly ash and/or bottom ash
- Ash generated in a lower-temperature ashing process
- Residual ash from Battelle’s coal liquefaction process
Making use of residual ash from coal liquefaction processes directly leverages work currently being conducted by Battelle for the U.S. DOE NETL and the OCDO entitled “Greenhouse Gas Emissions Reductions Research and Development Leading to Cost-Competitive Coal-to-Liquids Based Jet Fuel Production.”
Battelle’s Acid Digestion Process has the potential to concentrate the REEs in coal ash to a product of greater than 2% REEs by mass, while recovering greater than 90% of the nitric acid used. The proposed technology offers a number of benefits:
- The closed loop process is not expected to generate a significant waste stream, as the process chemicals and emissions are recycled within the process.
- The process produces a concentrated solid form of rare earth oxides for easy delivery to a REE purification facility.
- The process will identify coal sources expected to have higher availability of REE, thus allowing much higher recoveries of the rare earths, improving the concentration of the product and reducing the cost of the processing operation per ton of recovered REEs.
If these initial studies are successful, Battelle hopes to continue to develop the technology in Phase II of the NETL program. Successful execution would represent a significant breakthrough for the economic recovery of REEs from coal products.
Battelle scientists and engineers have also demonstrated a process that turns coal into jet fuel.