NETL’s overarching goals are to develop separation technologies that can be economically deployed to enable domestic supplies of rare earths, and to reduce environmental impacts during REE production from coal-based resources. NETL’s current goals are to validate by 2020 the technical and economic feasibility of prototype systems to produce high purity, salable REEs.
In-house Research at NETL
Rare earths are actually not that rare. However, it is unusual to find them in large concentrations. To overcome this hurdle, NETL’s in-house research is focusing on all stages of REE recovery from coal and coal-based products, including field sampling, characterization, separation and extraction, and computer modeling.
NETL developed techniques for characterizing samples returned from the field as well as produced in the lab. More than 800 field samples have been collected since June 30, 2015, by NETL in-house researchers and personnel from NETL’s headquarters – DOE’s Office of Fossil Energy. The United States Geological Survey and the Electric Power Research Institute have both signed memorandums of agreement with NETL calling for additional collaborative field sampling activity.
Rare earth characterization efforts by NETL are among the most advanced in the world. Researchers at the lab employ a variety of techniques, including digestion methods for the accurate determination of trace REE contents by inductively coupled plasma mass spectrometry – a technique that minimizes uncertainty in trace REE determination.
After determining what rare earths are present and in what quantities, the next step in obtaining the valuable materials involves separation and extraction techniques. NETL is developing these capabilities for use with coal‐based resources such as coal, coal refuse, clay and sandstone over- or under‐burden materials, aqueous effluents and power generation ash.
NETL’s multifaceted in-house research is helping to establish a reliable domestic supply of rare earths. The U.S. consumes around 16,000 to 17,000 tons of REEs each year, and this demand could be met by completely extracting rare earths from domestic coal and coal byproducts. For example, a typical coal sample contains 62 parts per million (ppm) of total rare earth elements on a whole sample basis. With more than 275 billion tons of coal reserves in the U.S., 17 million tons of rare earth elements are present within the coal.
NETL research engineer Evan Granite said, “By tapping into this vast untouched resource of coal and coal byproducts, the United States could benefit from a 1,000-year supply of REEs at the current rate of consumption.”
In addition, the U.S. typically produces around 100 million tons of coal fly ash annually and this ash typically contains more than 400 ppm of total rare earth elements. Clays and shales located above and below coal seams are also a possible source since they can contain around 200 ppm total rare earths.
External Partnerships to Accelerate REE Research
In fiscal year 2016-2017, congressional language expanded the REE program’s objectives to include external agency activities for development and testing of commercially viable advanced separation technologies at proof-of-concept or pilot-scale stages. The initiative called for near-term deployment of the innovations enabling the extraction and recovery of rare earths and minerals from U.S. coal and coal byproduct sources with the highest potential for success. To accomplish this, NETL reinforced its robust in-house research with partnerships in industry and academia. NETL federal project manager Charles Miller said, “The DOE-NETL REE program portfolio currently comprises 14 active external projects, and they are achieving remarkable success.”