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Show 1l 'e, & V;}~ 'Q (l~ ~~) ~~ /\ f~+ Pilot Evaluation of Reburning for Cyclone Boiler NOx Control H. Farzan and L. Rodgers, The Babcock & Wilcox Company, Alliance, Ohio G. Maringo, The Babcock & Wilcox Company, Barberton, Ohio A. Kokkinos, Electric Power Research Institute, Palo Alto, Califomia J. Pratapas, Gas Research Institute, Chicago, Illinois Presented to the American Flame Research Committee Pittsburgh, Pennsylvania, October 4 - 6, 1988 ABSTRACT RDTPA 88-40 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 stoichiometric conditions which convert NOx produced in the main combustion zone to molecular nitrogen, thereby reducing overall NOx emissions. This paper presents the encouraging pilot-scale results obtained using natural gas, fuel oil, and pulverized coal (PC) as reburning fuels. At a reburning zone stoichiometry of 0.9,67% NOx reduction for gas and oil reburning and 57% for coal reburning were achieved. Flue gas recirculation (FGR) was introduced at the reburning burners, and improved mixing and NOx reduction. FGR was more effective with PC reburning. Carbon monoxide (CO) emissions levels were low (less than 30 ppm) throughout the various optimum test conditions. Although the carbon content of the fly ash increased, the overall combustion efficiencies were insignificantly lower for all the reburning fuels. Furnace exit gas temperatures increased by less than 500F during reburning operation. The impact of reburning technology to full-scale cyclone boiler operation is currently under investigation. INTRODUCTION The Electric Power Research Institute (EPRI) and the Gas Research Institute (GRI) contracted with the Babcock & Wilcox Company (B&W) to perform a pilot- scale evaluation of the reburning technology for cyclone boiler NOx emissions control. These pilot tests were justified via a previous EPRI-sponsored (Project RP-1402- 30) engineering feasibility study ofreburning for cyclone boilers performed by B&W. The feasibility study revealed that the majority of cyclone-equipped boilers could successfully apply this technology in order to reduce their NOx emission levels by approximately 50 - 70% (1). The major criteria that substantiated this potential was that sufficient furnace residence time does exist within these boilers in order to apply the technology. Thus, based upon this conclusion, the next level of confrrmation pilot-scale evaluation was justified. These pilot tests involve evaluating the potential of natural gas, oil, and coal as the reburning fuel in reducing NOx emissions. This paper focuses on the results obtained during the evaluation of these three reburning fuels. 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 NO emitted since their inherent turbulent, high-temperature combustion process is conducive to NO x x formation. Although the majority of 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 1 |
