Scrubbing the air
Aug 6 - McClatchy-Tribune Regional News - Mike Meyers Star Tribune, Minneapolis
Every year, a power plant tucked amid the pines and resorts of Lake Superior's North Shore turns out enough electricity to power Duluth and Superior two times over. Most of that electricity sustains paper mills, taconite plants and thousands of jobs. The coal-fired power plant churns into the air 3,373 tons of nitrogen oxide, 5,538 tons of sulfur dioxide, 221 tons of carbon dioxide and 77 pounds of mercury each year. That stew of chemicals has been linked to illnesses, increased mortality rates, acid rain and global warming. And to all of that add 253 tons of tiny particles born of combustion. The 50-year-old plant has reached an age at which many industrial sites are nearing the end of their useful life. But Taconite Harbor is in the midst of a $54 million makeover. Minnesota Power's goal is to eliminate 55 to 90 percent of the pollutants the plants produces, before government gets around to pressing the point. Customers ultimately will pick up the tab. Minnesota Power estimates the cleanup will add about 0.7 cent to the cost of a kilowatt hour. The current rates range from about 4 cents a kilowatt hour for industrial customers to about 7.3 cents for residential electricity users. The move is getting mixed reviews from one environmental group, the Sierra Club. "It was an ugly, polluting pig until this upgrade," said Clyde Hanson, co-chairman, Sierra Club North Star Chapter Mining Without Harm Campaign. "The good news is they're substantially reducing their mercury emissions. They took the initiative," he said. "The bad news is that it's still a coal plant, creating gases that will contribute to global warming." Sensitive location As with any real estate, location matters. The Taconite Harbor plant, in Schroeder, is in an "air shed" that includes the Boundary Waters Canoe Area and Apostle Islands National Lakeshore in Wisconsin and two national parks, Voyageurs in Minnesota and Isle Royale in Michigan. "There's a lot of changing air regulations that are coming," said Allan Rudeck Jr., Minnesota Power vice president, generation. "The primary issue is regional haze." Duluth-based Allete Inc., parent company of Minnesota Power, decided to get ahead of regulators, state and federal, who are expected to impose tighter emissions standards, even though the rules may be years or decades in coming. For instance, the federal government wants all national parks to have pristine air quality -- close to where it was before the industrial revolution. That goal is set for 2062. Minnesota Power bought the plant from LTV's taconite operation in 2001 and hopes to keep it running indefinitely, rather than be forced to replace it at a potential cost of hundreds of millions or billions of dollars. The public benefit of emission reductions at Taconite Harbor and a sister plant in Hoyt Lakes is projected at $1 billion to $1.2 billion, in today's dollars, over decades to come. The benefits are to be shared by Minnesota residents and people living beyond the state's borders. It's part of a nearly $300 million program to clean up Minnesota Power plants, including projects at power plants in Cohasset and Hoyt Lakes. Improved public health, with lower medical costs and lower death rates, are the chief savings of the emission controls, according to the author of the estimate, the Minnesota Pollution Control Agency. New control combination An element that makes the smokestack cleanup unusual: It's using a combination of emission control technologies, never installed in concert, to blot up noxious chemicals before they can reach outside air. The job has been a challenge. Late last year, about 450 workers -- boilermakers, pipefitters, electricians and insulation specialists -- converged on Schroeder to punch holes in a steel boiler 160 feet tall. Then came the choreography of bringing in thousands of parts, from fans and air ducts to chemical injectors and conveyors to bring clean-up agents from a newly built storage building to the boiler. Catwalks wind between forests of metal. In some places, the temperatures are 30, 40, 50 degrees warmer than outside, even on a mild summer day. In all, workers had to juggle 50 tons of motors, rotors and other equipment into a building where boilers already took up much of the space. "Six months of engineering came ahead of that," said Jay Crilley, director of MobotecUSA, the company that designed and oversaw installation of the cleanup equipment. The final installation at the first of three boilers at the Taconite Harbor plant was finished in June as part of a six-week major maintenance shutdown that comes ever seven or eight years. The other two boilers at the plant will be modified next year. One of Mobotec's inventions, introduced in Sweden in 1990, is a device that removes mercury from smokestacks by injecting and circulating chemicals that absorb the heavy metal. The Taconite Harbor installation is the first time the company has tried to use mercury-reduction equipment in harmony with scrubbers to reduce nitrogen oxide, sulfur dioxide and carbon dioxide. A large job The cleanup gear is big because the job is tall. The plant burns 800,000 tons of coal per year inside boilers that reach 2,000 degrees. Granulated limestone, which helps absorb some of the pollutants, is injected into the boiler at a rate of 10,000 pounds an hour. The chemicals to reduce mercury emissions are pumped in at a rate of 500 pounds an hour. Inside the control room, video monitors show the flames swirling inside the boilers, which heat water that turns turbines to generate electricity. A conventional boiler flame is a carefully contained ball of fire. In the boiler with the pollution-control equipment, the video camera shows a faint jet of pollution-absorbing material being injected into the flames. The result is a whirlwind of flame that Rudeck said burns coal more efficiently than conventional boilers. The new technology has another virtue, he said. If something happens to trip up the pollution control gear, it doesn't shut down the power plant. "You can shut it on and off if there are problems and still run the plant," Rudeck said. "That's very valuable from the reliability viewpoint." Mike Meyers --612-673-1746 --meyers@startribune.com
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