The paper deals with the numerical prediction of a high swirling non-premixed confined natural gas diffusion flame in order to predict the pollutant emissions NO(x) using the PDF model coupled with the Reynolds stress model (RSM). A chemical equilibrium model in conjunction with the assumed shape of the PDF is adopted. The chemical combustion reactions are described by nine species and eight reactions [Westbrook CK, Dryer FL. Chemical kinetic modelling of hydrocarbon combustion. Progr Energy Combust Sci 1984:10:1-57]. The PDF of the mixture fraction is described with a p-function. In order to predict the NO, emissions, a NO, post-processor of the Fluent code has been performed. The concentration of O and OH radicals are obtained assuming the partial-equilibrium assumption and using a PDF in terms of temperature. The numerical simulation of various factors influencing the combustion process are examined and compared favourably with experimental results. (C) 2008 Elsevier Ltd. All rights reserved.