Interview: Coming Clean
Project to demonstrate potential of new mining technology
The M100 - Magnetic Elutriator, a new “taconite washing machine” developed by St. Paul-based 5R Research Inc., could put a whole new spin on separating iron ore from waste rock. The Iron Range Resources and Rehabilitation Board and others are funding a commercial-scale test of this new mining technology, which could extend and improve the productivity of northeastern Minnesota’s mines.
If successful, the $1.4 million pilot test of the unit could open the door to a faster, cheaper and more environmentally friendly way to recover iron ore particles from taconite.
In magnetic elutriation, electromagnets and carefully controlled water pressure agitate taconite slurry to separate ore from silica and other waste materials, similar to the way a washing machine’s agitator action loosens dirt from clothing. This would replace the two-step system of magnetic drum separators and chemical-laden flotation units currently used at most Iron Range mines.
John McGaa, president of 5R Research, estimates that elutriation could save the mines $1 per ton in energy and chemical costs and could increase production by up to 10 percent. “This is basically a $1 million experiment that, if it works, will be a super project for the mining industry on the environmental and economic fronts,” he said.
EVTAC Mining will be the first to test the M-100 magnetic elutriator— a 60-foot tall, 500-horsepower fiberglass tube outfitted with an electromagnet that will process 100 tons of slurry per hour. Construction will begin this summer; McGaa hopes to have the unit running by January 2001.
Pilot tests have shown that elutriation can recover more ore and produce a higher-quality product than traditional ore processing. Silica levels have averaged 3.5 percent, compared to EVTAC’s normal levels of 5.5 percent, and could be as low as 2 percent. Levels this low also could make direct-reduced iron (DRI) production feasible on the Iron Range. Ore recovery from elutriation has been about 99 percent.
Figures like these convinced the IRRRB to provide a $500,000 loan that could later be converted to stock in 5R Research.
“If this all works out, it’ll be a home run for the industry,” said Brian Hiti, the IRRRB’s manager of mining and natural resources development. “It’s a more productive way to do what they’re already doing, and it could make Iron Range ore acceptable for DRI.”
5R Research also was one of eight companies nationwide to receive a $500,000 grant from the Department of Energy through its National Industrial Competitiveness for Energy, Environment and Efficiency (NICE3) program. EVTAC is kicking in $280,000 and 5R has about $100,000 into the project.
A paradigm shift
Other aggregate production processes such as gravel-sorting have used elutriation for years. McGaa first applied it to mining while researching ways to recover the lead and iron in steelmakers dust — the vapor released from boiling steel. Ironically, his discovery was made using a demagnetizer, a unit that uses an electromagnet to demagnetize regular magnets. “In effect, magnetic elutriation works because we tried a demagnetizer,” McGaa said. “Nobody had thought about using a ‘demagnetizer’ to magnetize things.”
In the M100, an electromagnetic zone will magnetize the slurry just long enough to separate ore from waste products.
The taconite industry’s traditionally conservative approach to technology has slowed the acceptance of magnetic elutriation. Mines can be reluctant to make capital investments in new, unproven technology. “Wherever we went, early in the process, there was a little bit of disbelief. The feeling at the mines was that you couldn’t do separation as a one-step, single-pass process,” McGaa said.
This attitude makes 5R’s alliance with EVTAC all the more significant. “This project is unique because both the industry partner and the entrepreneur are very interested in commercial-scale testing,” Hiti said. “With these two elements and the DOE grant, we were able to come in with key support to help it succeed.”
Proving the potential
EVTAC’s management is optimistic about the project’s success. Two smaller elutriator pilot units have been tested at the plant during the last three years; each has run for a long time. “We’re comfortable with the technology, we just need to know if it will run at the scale we need,” said Howard Hilshorst, president of EVTAC.
Well-known industry vendors, including Westinghouse, Foxboro, GPI and Saloman Electric, are building the structure. Some of the components will be specially designed. “Electromagnets of this size have never been made for mining before,” said Gary Saari, senior facility engineer at EVTAC. “We all believe it should work, but there are always bugs to work out when new technology moves from small-scale to large-scale use.”
At least one of two units being installed will run 24 hours a day, seven days a week for about 18 months, starting in January; the other will be a back-up.
Time will tell if magnetic elutriation is a technology whose time has come. Whatever the result, one thing remains clear: a new cycle of mining technology has begun. “Taconite has to change. If we don’t get more efficient, we’re going to go away. This technology looks like a very viable means of lowering our silica levels and our production costs,” Hilshorst said.