Application of Reburning Technologies for NOx Emissions Control on Oil and Pulverized Coal Tangentially Fired Boilers

ENEL has initiated a comprehensive program to comply with air quality standards for fossil fuel fired thermal power stations in Italy that limit NOx emissions to 200 mg/Nm3 (corrected to 3% O2 for oil and gas, and 61 O2 for coal). Both in-furnace (combustion modifications) and post-combustion (e.g. SCR) technologies are being examined. This paper focuses on the in-furnace combustion modification technology of reburning as a means of providing substantial NOx emissions reductions for oil and pulverized coal tangentially fired boilers. Results are presented from testing in ENEL's 50 KWt laboratory scale test facility in Pisa. Italy, ABB-CE's 15-30 MWt pilot scale combustion test facility in Windsor, Connecticut, and ENEL's 35 MW, tangentially fired utility boiler in Sardinia, Italy. Presented data highlights maximum achievable NOx reductions for the varied reburn test parameters of reburn fuel (natural gas) quantity, reburn flue gas recirculation quantity and separated and close coupled overfire air quantity. Influence of furnace zone stoichiome tries (windbag, reburn, and burnout zones) on optimized reburn effectiveness is reviewed in detail. Impacts of reburn system operation on boiler performance are also discussed. Results show that reburning technology offers substantial NOx emissions reductions in tangentially fired boiler applications.