Abstract: This paper presents the results of a computational investigation on the effects of wall boundary conditions on the hydrodynamics of an annular fluidized bed (AFB). The objective is to develop better understanding of the hydrodynamics of an AFB, which are very complex as there are two wall surfaces with which the particles interact and fall along. The wall boundary conditions are investigated by varying the values of specularity coefficient. Simulations are performed using an open source code MFiX by employing the two-fluid model which considers solid and gas as the interpenetrating continua where the solid viscous stress tensor is calculated using the kinetic theory of granular flow. Geldart-B particles with a diameter of 530 μm and air as a fluidizing agent are used. A circumferential core-annulus structure is observed in the reactor. The hydrodynamics of AFB is very sensitive to the specularity coefficient. Low values of specularity coefficient produce high particle velocities in the bed as there is less loss of tangential momentum to the walls. However, the bed height predicted by all the values is found to be similar. Concerning the bubble statistics, it was found that low specularity coefficient values produce large bubbles usually in the form of slugs whereas as the specularity coefficient value is increased, small bubbles begin to form.