Since 1988 China has been the dominant supplier of rare earth elements (REE), providing 95 percent of the global market in 2011. To break their dependencies, countries around the world have been on missions to identify ways to extract these valuable minerals, and a Department of Energy (DOE) lab is among the players taking the lead in the U.S.’s efforts.
There is tremendous potential. In 2015, the U.S. produced about 900 million tons and consumed 798 million tons of coal. If 100 percent of the REEs were extracted annually from coal ash, it would meet the market demand for most industries that depend on it, according to the DOE.
Currently REEs are used in catalysts, cell phones, hard drives, hybrid engines, lasers, magnets, medical devices, televisions and other applications.
In search of metal extraction technologies
The DOE’s National Energy Technology Laboratory (NETL) is charged with identifying environmentally responsible ways to separate and recover REEs from coal and coal byproducts. It has issued funding for multiple projects in geographic locations where coal is abundant.
The U.S.’s coal resources not only provide opportunity to reduce dependency on foreign sources but opportunity to create new industries in regions where coal is plentiful, says Mary Anne Alvin, REE technology manager at NETL.
“A lot of coal ash is disposed of in landfills and ponds and to have another product come out of something that had not been thought of is exciting. As we see what separations we can do we can look at other avenues and uses,” she says.
For example, Republic Services Inc. last June unveiled an ash metal recovery facility at its landfill in Roosevelt, Wash. The facility processes all newly delivered ash to the Roosevelt Regional Landfill as well as the existing ash currently in the landfill.
Starting with low concentrations and scaling up
The goal of the Rare Earth Elements from Coal and Coal By‐Products program is to demonstrate if REE can be extracted. The pilot projects will begin by trying to extract low concentrations and eventually scale up to higher concentrations. Ultimately, the idea is to reach higher purity concentrations to meet certain specs to manufacture products in multiple industries.
The first DOE research projects focused on ash, but a now broader focus includes extraction and separation from nonash materials, which could be from pre-cleaned coal, clay, shales and other materials embedded in coal.
The University of Kentucky is among the government funding recipients, with the project led by Rick Honaker, professor of the university’s Mining and Engineering department.
The project’s ultimate goal is to develop, design and test a mobile pilot scale facility with capacity to recover one quarter ton an hour of REEs from coal and coal byproducts.
“We specifically focus on the precombustion side, looking at material before it’s put into a boiler to produce electricity. This is because when you put coal in a boiler at 2,000 degrees, the material becomes highly fused, meaning acids used to extract rare earths cannot penetrate components of the particles,” says Honaker.
The research team put rare earth metals in a solution to convert them from solids to liquids. Once they are liquid, other chemicals are used to extract rare earth metals from the solution and purify them.
“Our typical rare earth metal concentration is .03 percent of total rare earth metals that were contained in the feedstock sample,” he says. “Using this process, we could produce 10 percent rare earth oxide concentrate from that .03. That’s a 33,000 percent increase in what we could do before in a lab setting. So we are going from a small amount to producing commercial grade material. You now have a solution that can be commercially used to recover purified rare earth metals.”
Honaker thinks rollout of such technology is about four or five years out. But once it materializes, it could provide business opportunities for multiple stakeholders who have been unable to profit on low-density rare earth metals.
“Mining company Mountain Pass [in California] went broke for this reason,” Honaker says. “They were getting cents per kilogram for the rare earths they produced. The coal companies would be able to make money. The company who purifies rare earths would make money. And those building things like generators and solar panels will have material they can use as will the Department of Defense and defense industry.”
The University of Kentucky project is about to launch design of a pilot scale mobile processing facility for recovering rare earth metals to be able to move from one mining operation to another. The targeted goal is to start building in September 2017 and start testing late in 2018.