Enhancement of a Process Flowsheet for Recovering and Concentrating Critical Materials from Bituminous Coal Sources

  • R. Q. HonakerEmail author
  • W. Zhang
  • J. Werner
  • A. Noble
  • G. H. Luttrell
  • R. H. Yoon


Recovery of rare earth elements (REE) from coal-related resources has recently received significant interest due to supply concerns and their key roles in critical industries and defense-related technologies. An integrated flowsheet consisting of sorting, crushing/grinding, physical separation, acid leaching, solvent extraction, and selective precipitation was designed to achieve continuous production of rare earth products from various coal-related resources such as coarse refuse and acid mine drainage. A pilot plant was constructed that enabled continuous testing of the circuitry on a range of different coal-based feedstocks. Despite achieving significant success in producing high-grade rare earth oxide products, low REE recovery values and high operational costs necessitated a re-evaluation of the process flowsheet. This article describes the circuitry improvements that were based on both laboratory and pilot plant test results. Roasting as a pre-leach treatment was found to significantly improve the leaching rate and overall REE recovery values. After roasting West Kentucky No. 13 and Fire Clay coal refuse materials at 600 °C, REE recovery increased by 60 and 40 absolute percentage points, respectively. Rare earth concentration in the pregnant leachate solution (PLS) was increased to around 700 ppm prior to solvent extraction using a staged precipitation method. REEs in the precipitate were re-dissolved, purified, and extracted from the PLS using solvent extraction and selective precipitation to values of around 80%. As a result of the improvements, chemical consumption in the acid leaching and solvent extraction processes was significantly reduced. A techno-economical assessment of the improved flowsheet indicated significant commercialization potential.


Rare earth elements Coal Recovery Roasting Staged precipitation Techno-economical assessment 


Funding Information

This material is based upon work supported by the Department of Energy under Award Number DE-FE0027035.

Compliance with Ethical Standards

Conflict of Interest

The authors declare that they have no conflict of interest.


This report was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency thereof, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof.


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Copyright information

© Society for Mining, Metallurgy & Exploration Inc. 2019

Authors and Affiliations

  1. 1.Department of Mining EngineeringUniversity of KentuckyLexingtonUSA
  2. 2.Department of Mining & Minerals EngineeringVirginia TechBlacksburgUSA

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