Russian know-how cuts emissions at a U.S. power plant
Due to a new Russian technology, an 80-megawatt coal-fired boiler at Carolina Power and Light Company's (CP&L) Weatherspoon, N.C., plant is emitting about 35 percent less nitrogen oxides (NOx). NOx, emitted from all combustion processes, reacts with other chemicals in the atmosphere to form ground-level ozone, resulting in smog.
The technology, known as WIR, was developed at the St. Petersburg Polytechnic Institute and brought to the United States by North Carolina's Research Triangle Institute (RTI). WIR - loosely translated as "vortex" - is already operating in more than 20 coal-fired boilers in Central Europe, where companies are scrambling to reduce emissions despite limited funds for retrofitting existing boilers.
"We're interested in trying WIR in combination with technologies such as low-NOx burners, reburning and flue-gas treatment," said RTI's Dr. John Cleland. "As regulations tighten, companies will have to use other technologies such as SCRs selective catalytic reduction to remove NOx from their stack emissions. The more work you do in the boiler furnace with technologies such as WIR, the smaller those SCRs can be. That saves money, because SCRs are by far the most expensive NOx-reducing technology."
The CP&L demonstration of WIR is in a tangentially fired boiler shaped like a large, rectangular metal can. Burners on the boiler's furnace wall blow pulverized coal and air into the furnace at an angle, creating a spinning effect. This vortex produces efficient combustion.
The process involves re-aiming the burners and injecting new flows of air at the bottom of the boiler. These air flows produce a pair of horizontal vortices beneath the normal vertical one, creating a larger combustion region in which the coal remains for a longer time and burns at a lower temperature than normal. These conditions produce less NOx, without undue increases in other emissions such as carbon monoxide and fly ash.
Next, an oxygen-starved region forms in the lower part of the boiler furnace. In this region, the reaction chemistry breaks NOx apart, destroying potential polluting emissions.
For more information, contact RTI's Reid Maness at (919) 541-7044 or crm@tri.org.
This article originally appeared in the 10/01/1999 issue of Environmental Protection.
About the Author
Gerald F. Connell, ChE is a consultant, retired after 30 years with Capital Controls Group, Severn Trent Service Inc., Colmar, Pa. Mr. Connell is author of "The Chlorination/Chloramination Handbook," published by the American Water Works, and a forthcoming "Chlorination/Dechlorination Handbook" to be published by WEF.