It is important to determine the effect of operational parameters in CFB combustors via a simulation study instead of expensive and time consuming experimental studies. From this point of view, in this study a model for a CFB combustor, which can be employed to simulate under a wide range of operating conditions, has been developed. The developed model includes coal volatilization, attrition and combustion of a char particle. In the modeling, the combustor riser is analyzed in two regions: bottom zone considering as a bubbling fluidized bed and upper zone core-annulus solids flow structure is established. In the model, solids return cycle has been considered. Simulation model calculates the axial and radial distribution of voidage, velocity, particle size, pressure drop, gas emissions and temperature at each time interval for gas and solid phases. The simulation results are compared with test results obtained from various CFBC test rigs at different size and developed model has been validated.