The rate of conversion during gasification of char particles depends on the type of reagents, the concentration of reactants, and reactor temperature, among many other parameters; however, the overall conversion depends on the residence time distribution (RTD) of the particles in the reactor. The objective of the present work is to investigate the influence of gasifying agents, their concentration, and reactor wall temperature on the RTD of the char particles. The aim also includes studying the effect of mean residence time on the overall char conversion during gasification of Victorian brown coal in an entrained flow reactor. Two gasifying reagents, namely, CO 2 and H 2 O, are selected in the present study. A discrete particle model (DPM) is coupled with computational fluid dynamics (CFD) to simulate the solid phase dynamics. Gasification is modelled using a lumped approach. The mean residence time of the solid char particles, determined using three different methods, is observed to increase with the CO 2 concentration and wall temperature but decrease in the H 2 O environment. The longer residence time leads to higher overall char conversion in a CO 2 environment despite the higher reactivity of H 2 O compared to CO 2 as a gasifying reagent.