THE INFLUENCE OF NEAR BURNER REGION AERODYNAMICS ON THE FORMATION AND EMISSION OF NITROGEN-OXIDES IN A PULVERIZED COAL-FIRED FURNACE

Detailed measurements have been performed for two distinct pulverized-coal-fired burners in a large-scale laboratory furnace. Comparative in-flame data are archived and include gas temperature, O2, CO concentration, and an inventory of stable fuel nitrogen species and solids (HCN, NH3, N2O, NO, nitrogen release, mass flux, and particle burnout). A significant decrease in the NO concentration in the near burner region and a substantial decrease in the furnace exit values are observed when the "central tube" from a single annular orifice burner jet (normally the location of a gas or oil burner for light-up purposes) is replaced with a single central orifice burner jet of same cross-sectional area. The latter burner exhibits the delayed combustion phenomena normally associated with a tangentially fired system. The particle burnout remains unaffected due to the longer particles' residence time in the all-important oxygen lean internal recirculation zone. The difference in NO emissions is not reflected in the on-line N2O emission values that are found to be low (2-3 ppm) for both flames. Data recorded nearer to either burner configuration, however, reveal that the maximum N2O values for both burners are found in the flame region and are between 1%-2% of the corresponding maximum NO concentrations.