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Technology for recovering REEs from coal ash takes step forward

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World Coal,

In a project managed and co-funded by DOE Fossil Energy’s National Energy Technology Laboratory (NETL), an industry/academic research partnership has taken a significant step toward developing a pilot-scale test facility for creating a more effective way to harvest rare earth elements (REEs) from coal ash – a by-product of coal combustion, created when coal is burned to generate energy.

REEs are 17 elements on the periodic table that have significant value for national security, energy independence, and economic growth because they are used in high technology products such as catalysts, cell phones, hard drives, hybrid engines, lasers, magnets, medical devices, televisions, and other applications. The US has been importing REEs from markets dominated by other countries. The development of an economically competitive domestic supply of REEs from US coal and coal by-products will help to maintain our nation’s economic growth and national security.

Coal-fired power plants are major producers of coal ash. The components of the ash vary, depending on the type and origin of the coal. Major ingredients in coal ash include rare earth minerals and elements that remain after the coal is burned in the power plant boiler.

America’s vast coal resources contain quantities of REEs that can potentially reduce the nation’s dependence on other countries for these critical materials while creating new industries and jobs in regions where coal played key economic roles. To create innovative technologies that can harvest REEs from coal resources, NETL created collaborative research and development programmes.

REEs occur in low concentrations in coals and coal by-products. Trace amounts are measured in concentrations ranging up to 1000 ppm. In a project supported by NETL and using post-combustion coal ash as the feedstock, Physical Sciences, Inc. (PSI), in a partnership with the University of Kentucky Center for Applied Energy Research (UK/CAER) and Winner Water Services, produced a mixed rare earth product using a micro-pilot chemical processing system in its Andover, Mass. laboratory.

Starting with a 500 ppm rare earth concentration in the fine ash fed to the micro-pilot system, PSI made a product with greater than 50 000 ppm rare earth concentrations, or greater than 5% by weight a 100-fold increase in the rare earth concentration.

According to Charles Miller of NETL, PSI will first perform physical processing of ash from combustion of East Kentucky Fire Clay bituminous coal in a power boiler to produce a non-magnetic fine ash. Fire Clay coal has relatively high REE concentrations in some areas because it contains volcanic ash, which might have been the source of REEs.

PSI’s partner UK/CAER physically processed their first batch of ash in Lexington, KY to serve as feed for PSI’s micro-pilot-scale chemical digestion and extraction process.

“The fine ash fraction was fed to PSI’s micro-pilot system for chemical processing,” Miller explained. “Data and knowledge gained from PSI’s micro-pilot system testing will be used by Winner Water Services to design and build a pilot-scale chemical processing system in Sharon, Pa. with capacity to handle a half tonne of fine ash per day.”

The process is promising because PSI’s product concentration to date significantly exceeded its initial target of 2% by weight. Miller said the pilot-scale chemical processing should begin in 2019 and be complete by 31 March 2020.

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