The gas-solid flow in gas-solid bubbling fluidized bed was simulated by a combined approach of computational fluid dynamics (CFD) and the two fluid model (TFM)

based on the modified EMMS drag model. A new image processing method derived from image calibration was applied to study bubble characteristics with focus on overall and radial distributions of bubbles as well as bubble profiles in terms of averaged equivalent diameter

rising velocity

degree of sphericity

and bubble lifetime at various superficial gas velocity. The results showed that smaller bubbles most located at the bottom of beds and wall region whereas larger bubbles most located at the central region of beds. With increase of superficial gas velocity

the bed height were gradually increased and bubble profiles of the averaged equivalent diameter

the frequency of occurrence

the rising velocity and the lifetime were all increased except that the degree of sphericity was decreased. Nevertheless

once the superficial gas velocity increased to a certain level

its increase would no longer have any significant impact on the rising velocity.