The simulation strategy described in this paper provides an alternative to conventional CFD post-processing to estimate exhaust NOx emissions. The method first analyzes a conventional CFD simulation to specify temperature histories and mixing rates. The bulk flow patterns are then represented with an equivalent network of idealized reactor elements. Detailed reaction mechanisms are then applied over the reactor network. The analysis was able to depict all the important tendencies among the major intermediates and products from a selection of coals that spanned almost the entire rank spectrum, under reaction conditions that spanned the domain of stoichiometric ratio in p.f. flames. The main practical benefit of the mechanistic complexity is that simulations based on detailed mechanisms require far fewer parameter adjustments than conventional CFD simulations whenever different fuels are considered. (C) 2002 Elsevier Science Ltd. All rights reserved.