Computational Fluid Dynamics (CFD) has been applied in the simulation of non-catalytic partial oxidation (NC-PDX) of methane and scale up of natural gas reformers. An industrial reference reformer and a large scale virtual prototype were considered in this study. Benchmark simulations were performed using the presumed PDF model and the Eddy-Dissipation-Concept (EDC) model, respectively. The results show that the PDF model is sufficient and more suitable for an engineering level estimation and trend prediction of the reactions in a NC-PDX reformer. Simulations of a large scale prototype reformer were performed using the PDF approach. The predicted peak gas temperature and its relation to the burner parameters were examined numerically. The results suggest that decreasing the temperature of input streams does not necessarily delay the ignition of methane/oxygen mixture. It is verified that a relatively small nozzle can effectively shift the flame downward, and generate a strong recycle flow field in the reformer. (C) 2012 Elsevier B.V. All rights reserved.