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Show PAPER NO.19 Rebuming Scale-Up Methodology for NOx Control From Cyclone Boilers -* H. Farzan, R. A. Wessel, H. Sorv, R. K. Kim, and L. W. Rodgers The Babcock & Wilcox Company - Research and Development Division Alliance, Ohio 4460 1 G. J. Maringo The Babcock & Wilcox Company - Fossil Power Division Barberton, Ohio 44203 A. S. Yagiela The Babcock & Wilcox Company - Energy Services Division Barberton, Ohio 44203 ABSTRACT 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 Btulhr 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 modeling INTRODUCTION There are presently 105 operating, cyclone-equipped utility boilers representing approximately 14% of preNSPS coal-frred generating capacity (over 26,000 MW). However, these units contribute approximately 21 % of the NOx emitted since their inherent turbulent, high-temperature combustion process is conducive to NOx formation. Although most cyclone units are 20 - 30 years of age, utilities plan to operate many of these units for at least an additional 10 - 20 years. The potential of future acid rain control and the location of the majority of these units (midwest) eventually will target these boilers for NOx emission control. Cyclone-equipped boilers have a unique configuration which prevents application of standard 10w-NOx burner technology, i.e., the combustion occurs within a watercooled horizontal cylinder attached to the outside of the furnace. Furthermore, other conventional NOx reduction techniques such as two-stage combustion cannot be applied to the full extent due to associated cyclone furnace slag tapping and corrosion concerns. The use of selective catalytic reduction (SCR) or selective non-catalytic (SNCR) technologies offers promise of controlling NOx from these units, but at high capital and operating costs. Reburning is therefore a promising alternative NOx reduction approach for cyclone-equipped units at more reasonable capital and operating costs. Reburning technology involves injection of a second fuel into the main furnace (above the cyclone region) to produce a secondary combustion zone where a reducing aunosphere exists. These local chemical reducing conditions convert NOx to molecular nitrogen, thus destroying a portion of the NOx produced in the primary cyclone combustion zone. Since reburning can be applied to the cyclone while it is operating under normal oxidizing conditions, this technology merits development for ultimate commercialization. The U.S. Department of Energy (DOE) under its Clean Coal II solicitation is sponsoring Babcock & Wilcox (B&W) to perform a 100-MWe demonstration of the coal |