ABSTRACT Internal circulation of particles in a dual-chamber fluidised bed can be developed by applying air of unequal velocity at the bottom of each chamber. This internal circulation results in an energy transfer between the chambers which is desirable in several industrial applications. ANSYS-Fluent software is used in this paper to simulate the influence of bed particles on the flow behaviour of gas and solids in a dual-chamber fluidised bed. The results of the simulation are expressed as solids circulation rate (Gs ) and discharge coefficient (Cs ). Simulations show that Cs at the slot ranged from 0.50 to 0.60 whereas Gs in the reactor is significantly affected by varying the bed particles. The pressure difference (due to the difference in density) between the chambers develops the internal circulation of particles in the dual-chamber internally circulating fluidised bed. It was observed that the denser the bed material, the higher the internal circulation is along with the pressure difference near the slot, and vice versa. Therefore, it can be concluded that the ICFB’s performance does depend on the bed particle type.