- Cement trucks rumbled down
Minnesota Highway 135 all winter, delivering the nearly 5,000 yards of
concrete needed to support Mesabi Nugget’s giant rotary hearth. When
completed, the 180-foot diameter hearth will convert relatively low-grade
taconite ore into nuggets with an iron content of 96 percent.
“It’s like a big lazy susan with three drives,” Steve Rutherford, project
manager for Mesabi Nugget, said in describing the hearth.
Steel Dynamics Inc., based in Fort Wayne, Ind., and its partner, Kobe Steel
Ltd. of Japan, expect to invest $235 million in the nugget plant. The project
has been taking shape quietly near Embarrass on former LTV Steel Mining Co.
land. It would have been easier and less expensive to tackle the concrete work
in warm weather, but Jeff Hansen, Mesabi Nugget’s engineering manager, said
crews worked through the winter, using heaters and tarps, to keep the project
on track. Mesabi Nugget aims to begin full production by the second quarter of
The project remains on schedule and on budget, Rutherford said. Crews are
beginning to assemble the steel skeleton of the plant.
Despite the substantial progress, many Northland residents seem to be
unaware of it, said Adam Thompson, a lead man, taking bids and ordering
equipment for Mesabi Nugget. “I don’t think many people realize we’re already
building this plant,” he said. Conrad Schumacher, an electrical engineer from
Embarrass, viewed Mesabi Nugget with a healthy dose of skepticism before he
came to work on the project. “My attitude was that I’ll believe it’s going to
happen when they start handing out applications,” he said.
Thompson, a Virginia resident, said fellow Rangers know better than to
count on projects coming to pass. “I think most everyone is hesitant, because
we’ve all seen so many ups and downs,” he said. “We’ve seen projects fall
In fact, that nearly happened to Mesabi Nugget in 2006, when
Cleveland-Cliffs Corp., then a partner in the project, withdrew its support.
With environmental permits for the plant about to expire in January 2007,
Steel Dynamics and Kobe Steel decided to push the project forward themselves.
The plant being built is expected to produce 500,000 metric tons of iron
nuggets annually. Initially, the processing operation would employ 50 to 65
people and an adjacent mine another 50 people. But if the facility performs as
anticipated, Steel Dynamics will seek permits to expand the operation,
Rutherford said. Based on current demand, he believes Mesabi Nugget could
triple its original size in short order.
An expanded operation probably would employ 250 to 300 people between the
plant and mill, Hansen said.
Schumacher said he wouldn’t be surprised to see six solid years of
construction on the site if Mesabi Nugget grows as expected. With detailed
design work already in hand and the benefit of experience, Rutherford is
optimistic Mesabi Nugget could build another unit for 10 percent to 20 percent
less than what it will spend on its first rotary hearth. That would drop the
cost of the next unit to between $188 million and $212 million, unadjusted for
The economic model for the project was built around an assumption that
nuggets from the plant would sell for $350 per ton. However, Rutherford said
the nuggets, which are akin to pig iron, would fetch more than $650 per ton
today, making for a much more profitable operation.
Thompson enjoys having a front-row seat as the first major new mining
development on the Range in years takes shape. “This will be the first
large-scale nugget plant of its kind in the world, so in a way, we’re watching
history being made,” he said.
Taconite pellets are fed into blast furnaces to produce steel, but the
nuggets, which are nearly pure steel, can go directly into electric arc
furnaces. Hence, nuggets will open a new market for low-grade Minnesota iron
Rutherford said the nugget operation offers environmental advantages, as
well. Kobe Steel reports its nugget system has been shown to produce 23
percent less carbon dioxide than a conventional blast furnace setup. Because
the nugget plant does not require a coke oven or a sintering plant, it also
produces less nitrogen oxide, sulfur dioxide and fewer particulates.
The nugget-making process begins with the formation of what are called
“carbonaceous green balls.” These are formed by molding iron concentrate from
taconite together with pulverized coal. The coal accounts for about 50 percent
of the green balls’ volume and 20 percent of their weight. The green balls
then are fed into a rotary hearth that turns and heats them to 2,600 to 2,700
The carbon in the coal reacts with iron oxide in the green balls, and after
six minutes in the rotary hearth, the iron melts, and slag separates from the
molten metal. The slag removal and reduction is completed within about eight
to 10 minutes of a green ball’s introduction to the hearth.
The process is energy intensive. Mesabi Nugget expects to buy 25 megawatts
of electricity from Minnesota Power when it begins production, and that
consumption could grow to 75 megawatts if the plant is built out to 1.5
million metric tons. “It’s sort of like baking cookies,” Rutherford said. “As
you bake them [the green balls], they begin to flatten out and become plastic.
The slag runs off, and you have a nugget.”
Although Mesabi Nugget already holds the permits it needs to build a nugget
plant, it still needs permission from the Minnesota Department of Natural
Resources to begin extracting ore from the former LTV property, last active as
a mine about seven years ago. The company will need to prepare an
environmental impact statement and undergo a thorough review before it can
mine the site.
From the Duluth News Tribune