NEW YORK, Jan. 29 (UPI) -- Microwave ovens can be used to make a high-quality steel that potentially is cheaper and cleaner than steel made in modern blast furnaces, Michigan scientists reported.
Researchers said their new method could slash steel production costs by as much as 50 percent, benefiting U.S. heavy industry, particularly in the Great Lakes region, where the steel and auto industries are centered.
U.S. steel production has dropped from 130 million tons in 1976 to about 90 million tons last year -- compared with a total world output of about 870 million tons annually. The U.S. iron and steel industry currently is worth $57 billion, according to federal estimates.
"More than 30 steel mills bankrupted in the last four years, including longtime familiar names such as LTV, Bethlehem, National, Weirton, Geneva, and Rouge," said researcher Jiann-Yang Jim Hwang, director of the Institute of Materials Processing at Michigan Technological University in Houghton.
"We used to have three iron ore mines in Michigan's upper peninsula," Hwang told United Press International. "Two of them have been shut down recently. This has great impacts on our local economy because iron ore mining is the biggest industry in the region.
"There are a lot of layoffs. Young people have to leave home because of the lack of job opportunities. House values dropped by more than 50 percent. We need to do something about this," Hwang said.
Despite its decline, Hwang said, steel is the backbone of U.S. manufacturing.
"Our automobiles are about 66 percent weight in steel. Our machines are made mostly of steel. The buildings are made with large amounts of steel. Our military relies on steel. When we lose our steel industry, the impact is not going to be limited," he said.
The prototype device wired together microwave emitters, or magnetrons, from six garden-variety microwaves into one super-heavy-duty oven and added an electric arc furnace. When iron oxide and coal are placed inside, the microwaves trigger chemical reactions that reduce the iron ore to iron in a matter of minutes. The electric arc furnace then smelts the iron and coal into steel.
"With a blast furnace, most of the heat escapes," Hwang said. "It's like the stove in your home, where most of the heat warms your kitchen. It's inefficient. In our microwave, iron oxides can be heated to 1,000 degrees Celsius in one minute, compared to hours for conventional heating."
In addition to energy savings, the mega-microwave uses coal, eliminating the need for the high-cost coke normally used to make steel. The microwave process also is comparatively simple, cutting the number of steelmaking steps in half. It is friendlier to the environment, with significant reductions in emissions of acid-rain-linked sulfur dioxide and of the global-warming greenhouse gas, carbon dioxide.
"This technology shows a lot of promise," industry analyst Bruce Kettunen of Noramco Engineering in Hibbing, Minn., told UPI. "The big advantages of this process is, No. 1, it's based on coal and electricity, both of which the U.S. has plenty of. It's potentially able to use Western coal, which is inexpensive and low-sulfur. It also appears to produce a very good product -- comparable to pig iron or better -- which is what a blast furnace produces."
Kettunen said the process, which uses raw iron, is a natural fit with the iron ore industries of Michigan and Minnesota.
"This could be a promising technology, particularly for helping us re-use byproducts that are currently being discarded," said environmental engineer Mark Conedera of U.S. Steel Corporation in Pittsburgh.
There currently are two basic routes for steel production. In the first, so-called integrated mills use blast furnaces to produce high-quality steel from iron ore to manufacture items such as automobile parts. The second involves mini-mills, which employ electric arc furnaces to render steel scraps into generally low-quality steel for products such as I-beams.
"Nearly all the bankrupted companies are integrated mills. Our mini-mills grew from 10 million tons in 1976 to about 46 million tons today. Our integrated mills shrunk from 120 million tons in 1976 to about 44 million tons. Imported steel grew from 5 million tons in 1976 to over 35 million tons," Hwang said. "We are losing the game because our iron ore is not matching the need of the integrated mill technology and environmental regulations have caused the shutdown of many coke making facilities."
Blast furnaces get their name from the fact that air blasts from the bottom of the furnace. This means they cannot work with small ore particles, which would get blown around. Foreign iron ore from places such as Brazil or Australia is naturally very pure, and can be shoveled into blast furnaces with little fanfare. U.S. iron ore is not so pure, so it must get broken down to remove impurities, and then sintered back into larger particle sizes.
The microwave oven can work with small ore particles, thus potentially saving the industry the expensive step of sintering small U.S. ore grains into larger ones. While purifying local ore incurs costs, transporting ore via ship to the United States also is pricey, Hwang said.
The research currently is funded by a Department of Energy grant but Hwang said: "The funding is about exhausted and we don't know the federal budget situation for the steel program in DOE in the future. We hope our steel industry will open their arms to give this technology an opportunity to grow. If funding is not an obstacle, I think implementation is possible in three to five years."
The prototype device works on the experimental scale of pounds.
Mini-mills such as Nucor's in Charlotte, N.C., could benefit from this technique because they already have electric arc furnaces, Hwang said.
"Now it is possible for them to improve the quality of their steel and expand their market share to the high end using cheap iron ore," he added.
Although Nucor is the largest U.S. steel producer, with more than $4.1 billion in sales annually -- as well as the nation's largest steel recycler, processing more than 13 million tons of scrap annually -- Hwang said the price of scrap used by mini-mills has almost doubled in the past few months, which has cut profits significantly.
"Integrated mills will have to make tough decisions," he said. "Currently, they have the best technology for forming and finishing. They can produce the highest quality sheets, plates, strips, bars, tubes and so on. However, their blast furnace operations are simply not competitive. Replacing the blast furnace portion may give them new opportunities."
Iron ore companies such as Cleveland Cliffs Iron, the largest supplier of high-quality iron ore pellets in North America, which sells nearly all its pellets to integrated mills, also could benefit, Hwang said. Likewise, foundries could benefit "because the cost of iron and steel affects them the most."
A competing technology to the microwave method is called the direct reduced iron method from Midrex Technologies in Charlotte, N.C., a subsidiary of leading Japanese steelmaker Kobe Steel in Tokyo. The DRI process does not produce steel, but rather provides high-purity iron for steel plants.
"Many DRI plants have been built," Hwang noted. "However, this technology uses natural gas."
He said because of the jump in prices for natural gas "many DRI plants have been idled. For example, Rouge Steel had its DRI plant shut down. CCI built a DRI plant in Trinidad -- this plant was shut down as well."
Microwave technology, which can be powered by a variety of energy sources, "will provide better insurance for the industry," Hwang noted.
Whether microwaves can find their way into steel depends strongly on the industry, Kettunen said.
"The industry just went through a horrible three or four years. I don't think anybody in the industry has a lot of money to spend on speculative processes," he cautioned. "The process needs to be developed one more step, so you can put numbers to see if it makes commercial sense. They've demonstrated that it works, now they have to demonstrate it works economically."
Upper Peninsula Steel, in Ishpeming, Mich., has licensed the microwave technology and is looking for partners.
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Charles Choi covers research for UPI Science News. E-mail [email protected]
