With the support of the National Energy Technology Laboratory (NETL), researchers from the University of North Dakota (UND) and Pacific Northwest National Laboratory (PNNL) identified unique pathways and pretreatments to extract rare earth elements (REEs) from low-rank coal (LRC) ash.
LRCs such as lignites are one of the most abundant fossil fuel sources in the world. To understand the forms, associations, and partitioning of the REEs, along with other relevant elements and minerals in the ash samples, as well as their ash chemistry, mineralogy, and morphology, the research team conducted an extensive characterization effort.
Researchers produced a mixed REE concentrate that was greater than 2 percent by weight using ash samples from full-scale power generation stations and a pilot-scale combustion system at UND. The sequential extraction methods utilized by UND and PNNL are tunable and can be adjusted to accommodate the differences in LRC ash chemistries and physical properties for recovering REEs with maximum processing efficiency.
“NETL supports several research projects throughout the Nation with the goal of finding affordable ways to obtain the rare earth elements we need to keep our economy going,” said Anthony Zinn, NETL’s project manager. “The extraction method developed at UND offers a degree of flexibility which may make it attractive for potential users in the future, allowing the economy to grow while also disposing of fly ash from our existing coal-based power plant fleet.”
The researchers determined that if higher levels of REEs were in the initial LRC ash, the process could be economically viable even without further optimization, as long as additional high-value metals or critical minerals were recovered. Additionally, a simple water wash pretreatment of the samples can reduce the required amounts of acid for initial REE extraction from lignite ash. The pretreatment reduces costs and adverse environmental impacts while improving worksite safety.
This flexible REE extraction method was an outcome of a NETL-funded cooperative agreement intended to develop a domestic supply chain for REEs. REEs are vital for manufacturing personal electronics, energy infrastructure and defense technologies, and many other high-tech applications.
NETL is a U.S. Department of Energy National Laboratory that produces technological solutions for America’s energy challenges. From developing creative innovations and efficient energy systems that make coal more competitive, to advancing technologies that enhance oil and natural gas extraction and transmission processes, NETL research is providing breakthroughs and discoveries that support domestic energy initiatives, stimulate a growing economy, and improve the health, safety, and security of all Americans. Highly skilled men and women at NETL’s sites in Albany, Oregon; Anchorage, Alaska; Houston, Texas; Morgantown, West Virginia; and Pittsburgh, Pennsylvania conduct a broad range of research activities that support DOE’s mission to advance the national, economic, and energy security of the United States.