This article presents a 3D full-loop computational fluid dynamics (CFD) simulation of a circulating fluidized bed gasifier (CFBG). The simulation results are validated against the experimental data and found to be in good agreement. Thereupon, the effect of the process parameters, ie, temperature, pressure, air/coal (A/C) ratio, and steam/coal (S/C) ratio, on the performance of the gasifier is analyzed. The effect of temperature on the hydrodynamics was found to be small. The CO and H(2)increase, whereas the CO(2)and H2O decrease with an increase in temperature. While the effect of pressure on the outlet species mole fraction is negligible, the gas and solid axial velocity decrease with an increase in pressure. With an increasing A/C ratio or decreasing S/C ratio, the combustion products (CO(2)and H2O) increase, whereas the gasification products (CO and H-2) decrease due to the increase in the O(2)concentration. In addition, temperature increases with an increase in the A/C ratio or a decrease in the S/C ratio. The feed velocity increases with an increasing A/C or S/C ratio, and, accordingly, the pressure increases and bed height decreases. The CH(4)decreases in all of the cases as it is being consumed in gasification as well as combustion reactions.