Reburning Scale-Up Methodology for NOx Control From Cyclone Boilers

There are currently no commercially demonstrated combustion modification techniques for cyclone boilers which reduce NOx emissions. The emerging reburning technology offers cyclone boiler owners a promising alternative to expensive flue gas cleanup techniques for NOx emission reduction. Reburning involves the injection of a supplemental fuel (natural gas, oil, or coal) into the main furnace in order to produce locally reducing conditions which convert NOx produced in the main combustion zone to molecular nitrogen, thereby reducing overall NOx emissions. After obtaining encouraging results from engineering feasibility and pilot-scale proof of concept studies (1)(2), Babcock & Wilcox is presently performing a U.S. Department of Energy Clean Coal II project to demonstrate the cyclone coal reburning technology on a full-size utility boiler. The host site for the demonstration is the Wisconsin Power & Light's 100-MWe Nelson Dewey Station. This paper describes the scale-up methodology from a 6-million Btu/hr pilot-scale facility to the Nelson Dewey station. This methodology involves: • pilot-scale evaluation with the demonstration coal • baseline measurements at the host site boiler, including velocity and temperature profiles, combustion, and emissions characterization • mixing optimization utilizing physical and numerical modelin