Rare Earth Elements (REE) Recovery from Coal Ash
Under internal research and development (IRAD) and small business innovation research (SBIR) funding, a PSI team developed a unique process to extract rare earth elements from coal ash, an abundant waste material produced in coal fire power plants. There are billions of tons of coal ash landfilled in the United States. A key feature of the PSI process is the use of landfilled coal ash to produce a viable cement substitute material.
REE Pilot Plant
As a part of this effort, the PSI team has worked with several university, utility and commercial collaborators (including Winner Water Services) to construct and operate a pilot plant that demonstrates the PSI process. The plant was first commissioned in 2020, and as of 2022 processes a half ton per day of coal ash. The output of the plant is a rare earth oxide concentrate that achieves greater than ninety percent purity.
This one-of-a-kind plant was a first for PSI, in that we took a chemical process performed in beakers and test tubes, and brought it all the way to the pilot scale. The next steps are to work with our government, academic, utility, and commercial partners to scale-up the operation further, process many tons of coal ash, and produce as much rare earth material as possible.
Rare Earth Elements (REEs) are used in a variety of applications including electronics. There are coal deposits in the United States with high total content of REEs. Our process involves a physical separation stage of the coal ash, followed by a chemical separation stage. This process has been demonstrated on the laboratory bench scale, and scaled-up to the pilot plant scale (0.5 tons per day of coal ash processing).
Left: In this area of the plant, coal ash is fed to the leeching tank where REEs are separated from the feed by filtration.
Right: Image of coal ash.