A 'reburn chemistry' modelling method for predicting the reduction of nitrogen oxide emissions in coal combustors is presented. The model is applied to predict NO, reductions in a large-scale laboratory pulverised fuel combustor with gas as well as coal reburn strategies. Extensive validation is performed in order to establish the model effectiveness through a range of furnace conditions and reburn configurations. The results obtained show good overall agreement with detailed in-flame experimental data including the trend of NO emissions reduction with the reburn zone air/fuel ratio. (C) 2003 Elsevier Ltd. All rights reserved.