The aim of this investigation has been to model combustion under suspension fired conditions in O-2/N-2 and O-2/CO2 mixtures. Experiments used for model validation have been carried out in an electrically heated Entrained Flow Reactor (EFR) at temperatures between 1173 K and 1673 K with inlet O-2 concentrations between 5 and 28 vol.%. The COal COmbustion MOdel, COCOMO, includes the three char morphologies: cenospheric char, network char and dense char each divided between six discrete particle sizes. Both combustion and gasification with CO2 are accounted for and reaction rates include thermal char deactivation, which was found to be important for combustion at high reactor temperatures and high O-2 concentrations. COCOMO show in general good agreement with experimental char conversion profiles at conditions covering zone I-III. From the experimental profiles no effect of CO2 gasification on char conversion has been found. COCOMO does however suggest that CO2 gasification in oxy-fuel combustion at low O-2 concentrations can account for as much as 70% of the overall char consumption rate during combustion in zone III. (C) 2011 Elsevier Ltd. All rights reserved.