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Mesabi Nugget pushes sustainable steelmaking forward

Keywords: Tags  Steel Dynamics, Kobe Steel, Mesabi Nugget,


Mesabi Nugget LLC in recent years began production of a marble-sized iron pellet that observers call the most revolutionary new iron-making process in half a century.

"The Mesabi nugget is a really, really nifty product," said Peter Kakela, professor of resource development at Michigan State University in East Lansing. "Larry Lehtinen, who spearheaded the project, always said that the second most exported commodity from Minnesota is the oxygen that is locked up in the iron ore pellets. The iron nugget project simply takes the oxygen out of the pellet."

Fort Wayne, Ind.-based Steel Dynamics Inc. (SDI), parent of Mesabi Nugget, partnered with Japanese steelmaker Kobe Steel Ltd. to pioneer the world’s first commercial-scale iron nugget operation. The $275-million facility at Hoyt Lakes, on the east end of Minnesota’s Mesabi Iron Range, uses Kobe Steel’s patented ITmk3 ironmaking process to convert "dry balls" of iron fines, pulverized coal, fluxes and binders into 3⁄8-inch iron nuggets using a direct-reduction process in a natural-gas-fired rotary hearth furnace. The pellets are 96- to 98-percent pure iron, with the remainder primarily carbon.

"We’ve gone from 65-percent iron with taconite pellets to 97-percent iron with Mesabi nuggets," Kakela said. "They are able to make steel cheaper and cleaner with the nuggets. They are shipping a higher-quality product that can go into the EF (electric-arc furnace) at the mini-mill as well as into the blast furnace."

Kakela noted that the gain in sustainability with commercial-grade iron nuggets is equal to the gains made half a century ago when the steel industry adopted a pioneer taconite processing technology in the Lake Superior iron ore fields. For most of the late 19th and early 20th Centuries, the industry had shipped several billion tons of rich, red natural hematite ore to the open hearth and blast furnaces that stretched from Chicago to Pittsburgh. By the 1950s, however, the industry was worried about the depletion of the Minnesota and Michigan iron ranges. Work done at the University of Minnesota by Edward W. Davis introduced a method of processing taconite, a plentiful low-grade ore that had never been utilized in the domestic steel industry. From the late 1950s to the early 1970s, the industry spent billions of dollars to build taconite pelletizing facilities in Minnesota and Michigan.

"It was the salvation of the U.S. iron industry," Kakela said. "The pellets used a little more energy at the mines but they more than overcompensated on the blast furnace side."


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