Dec. 16, 1998 GRAND FORKS, N.D. -- A radical leap forward in energy generation technology could significantly reduce emissions of carbon dioxide (CO2), a greenhouse gas, by using high temperatures to produce electricity far more cleanly and efficiently than current technologies.
While operating a high-temperature advanced furnace, researchers at the University of North Dakota Energy & Environmental Research Center (EERC) believe a world record was set for coal-fired power systems when pressurized air heated to 2,000 degrees Fahrenheit was produced. In an operating power plant, the hot air would have been used to spin a turbine and electrical generator.
"The highest temperature that we can find on record in scientific sources is 1,800 degrees Fahrenheit," says John Hurley, an EERC senior research manager.
A team led by United Technologies Research Center (UTRC), East Hartford, Conn., has designed a high-performance power system (HIPPS) that could provide up to a 60 percent increase in energy efficiency and be 90 percent cleaner than today's coal-fired power plants. The high-temperature advanced furnace, a component integral to HIPPS, is undergoing tests at the EERC. The next scheduled tests will take place in January 1999. The project is funded through the U.S. Department of Energy (DOE) Combustion 2000 Program and managed through the DOE Federal Energy Technology Center.
"I don't know of any other coal combustion technology that heats air to the temperature we're using," says Dan Seery, senior program manager at UTRC. "The fact that we got up to 2,000 degrees exceeds UTRC's and DOE's expectations. It shows that we could potentially increase power plant efficiencies from around 35 percent into the upper 50 percent range."
The substantial increase in efficiency of a high-temperature furnace means that a coal-fired power plant using HIPPS technology would use less coal, resulting in a one-third reduction in CO2 emissions. "This is the most efficient design available to reduce CO2 emissions well below the levels being discussed internationally," Hurley says.
Besides conserving natural resources and reducing CO2 emissions, HIPPS technology offers other environmental and economic benefits. It will incorporate the latest advances in pollution control technology to reduce emissions of sulfur dioxide, nitrogen oxide and ash by 90 percent. These pollutants have been linked to acid rain and human health problems.
HIPPS has been tested with various types of coal, but it can also be configured to use a variety of fuels. "It could run on biomass fuels, which include fast-growing trees and grasses, municipal waste or liquid fuels. Any type of fuel you can get into the furnace, you can use," Seery says.
Another advantage of HIPPS is that it can be retrofitted in older power plants for less than the cost of building a new conventional coal-fired plant. Also, the glassy by-product the furnace produces from the molten ash it creates has potential for use as an industrial abrasive material.
To meet the goals of Combustion 2000, HIPPS uses extremely hot, pressurized air that's blown through a turbine. The turbine spins a generator to make electricity. In today's power plants, steam is heated to 1,000 degrees Fahrenheit and sent through a turbine. HIPPS improves efficiency by eliminating the need to produce steam. Until now, the limitation in conventional power plants has been that steel steam pipes will soften and corrode at temperatures above 1,000 degrees. The breakthrough came when UTRC developed a method to weld a special alloy capable of withstanding intense heat. The company also helped develop ceramic tiles that can survive the heat and extremely corrosive environment inside the furnace, preventing destruction of tubes made from the alloy. As a subcontractor working with UTRC, the EERC developed a small-scale plant in which to test the high-temperature furnace and the innovative materials that make it work.
This, in turn, required some innovation by the EERC's engineers and plant operators. Although the furnace system is 30 feet tall, 6 feet in diameter and weighs 16 tons, it's a fraction of the size of a full-sized, commercial-scale power plant. However, it's also the largest, most complex combustion system the EERC has operated in its 47-year history.
"We had to develop many of our own components to build a system that would function at this scale," says Greg Weber, an engineer and EERC senior research advisor.
The EERC worked with the Chicago-based Plibrico Company to develop a special furnace liner (refractory) that prevents heat from escaping and resists corrosion by coal slag. Engineering solutions were developed by EERC staff to cope with problems ranging from molten ash (slag) cooling too quickly and plugging the furnace to developing and installing mufflers that substantially reduce noise while the system is running.
The EERC's plant operators played a major role in getting the system running by pouring the furnace refractory and erecting the structural steel in the Center's Technology Demonstration Facility. Butch Riske, EERC supervisor of combustion operations, says that despite the high temperatures the furnace generates and the complexity of HIPPS technology, it's not difficult to run.
"Actually, it's been one of the easiest units we've ever operated. The system is so automated that it can be run almost entirely from the control room," he explains.
How do EERC researchers feel about working on a technology that sets world records and has the potential to significantly reduce greenhouse gas emissions?
"On a day-to-day basis, I focus on the technical aspects, but I'm also interested in this technology's long-term potential to reduce the consumption of fossil fuels," Weber says. "I'd like to be involved in the next phase of this project when it moves from the experimental level to the demonstration scale."
EERC Director Gerry Groenewold says, "This is the type of technology that will not only contribute to a cleaner, healthier environment worldwide, but will also create high-tech jobs in the energy and environmental fields. As the EERC helps move HIPPS technology toward demonstration and then commercialization, one of our goals will be to assist in training people how to use it."
DOE awarded UTRC a prime contract for approximately $35 million (including a 25 percent cost-share from participants) for the second phase of Combustion 2000. UTRC has one of two competing technologies in development under the project. As a member of UTRC's Combustion 2000 project team, the EERC was awarded a subcontract of approximately $6.7 million over four and a half years to develop and test key components of the high-temperature furnace.
Groenewold commended U.S. Sen. Byron Dorgan (D-N.D.) for his efforts to maintain funding for Combustion 2000 research at the EERC. "This is an extremely important technology, one that will address issues related to resource conservation, energy efficiency, global climate change and the control of pollutants that damage the environment and human health," he says.
The project has also received support from North Dakota's lignite coal industry. The North Dakota Industrial Commission provided $262,510 research funding to test two types of lignite in the EERC's high-temperature furnace. An additional $175,057 was provided to the project through the EERC's Jointly Sponsored Research Program with DOE.
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