Oxy-fired coal combustion is a promising potential carbon capture technology. Predictive CFD simulations are valuable tools in evaluating and deploying oxy-fuel and other carbon capture technologies either as retrofit technologies or for new construction. However, accurate predictive simulations require physically realistic submodels with low computational requirements. In particular, comprehensive char oxidation and gasification models have been developed that describe multiple reaction and diffusion processes. This work focuses on the sensitivity of a recent comprehensive char conversion code named CCK, which treats surface oxidation and gasification reactions as well as the processes such as film diffusion, pore diffusion, ash encapsulation, and annealing. In this work the CCK code was adapted for the conditions of an oxy-coal system and subjected to global sensitivity analysis techniques in an effort to rank fundamental input parameters in order of importance. Comprehensive char conversion codes have dozens of fundamental parameters, some of which are not well-defined. Global sensitivity analysis was used to identify the most important submodels in order to direct additional research on model improvement. Results of this analysis showed that the annealing model, the oxidation reaction order, the swelling model, and the mode of burning parameter are the most influential and therefore prime candidates for improvement.