Numerical analysis of pulverized coal combustion characteristics using advanced low-NOx burner

A three-dimensional numerical simulation is applied to a pulverized coal combustion field in a test furnace equipped with an advanced low-NOx burner called Cl-alpha burner, and the detailed combustion characteristics are investigated. In addition, the validities of the existing NOx formation and reduction models are examined. The results show that a recirculation flow is formed in the high-gas-temperature region near the Cl-alpha burner outlet, and this lengthens the residence time of coal particles in this high-temperature region, promotes the evolution of volatile matter and the progress of char reaction, and produces an extremely low-O-2 region for effective NO reduction. It is also found that, by lessening the effect of NO reduction in Levy et al.'s model and taking the NO formation from char N into account, the accuracy of the NO prediction is improved. The efficiency factor of the conversion of char N to NO affects the total NO concentration downstream after the injection of staged combustion air. (C) 2004 Elsevier Ltd. All rights reserved.