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, O 2, CO concentration, and an inventory of stable fuel nitrogen species and solids (HCN, NH 3, N 2O, 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 N 2O 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 N 2O values for both burners are found in the flame region and are between 1%–2% of the corresponding maximum NO concentrations.