Abstract: The effects of operating conditions on the gas-solid hydrodynamics in a high-density CFB are numerically studied using the computational particle fluid dynamics approach. With the increase of standpipe bottom aeration rate, the solids circulation rate increases within the range of stable operation, while the packed bed height in the standpipe decreases. The same tendency is found for the standpipe aeration rate, however, it is more efficient than the bottom aeration rate to increase solids flux. With the increase of the solids inventory, the solids flux shows a parabolic relation with it, however, the standpipe pressure drop increases almost linearly under the fixed aeration conditions. The riser flowrate has only small effect on solids circulation behavior. The aeration distribution in the valve has little influence on solids flux, however, it affects significantly the valve pressure drop and transient flow behavior. The number of aeration ports on the standpipe does not influence solids flux much, but it affects the hydrodynamics stability of the standpipe.