In this paper fluidization transition from Geldart B to A induced by change in temperature was visualized by high-temperature electrical capacitance tomography (ECT) recently developed. Silica particles with a Sauter mean diameter of 222 μm and density of 2650 kg/m3, which are typically Geldart B particles at ambient condition, were fluidized in a fluidized bed of 5 cm from 20 to 600 °C. With the increase in temperature, ECT images showed the decrease in superficial gas velocity corresponding to the onset of bubbles, i.e. the minimum bubbling velocity (Umb) and homogeneous fluidization regime. The pressure drop versus superficial gas velocity curves confirmed the existence of homogeneous fluidization between the minimum fluidization velocity (Umf) and Umb at elevated temperature. Our detailed analysis confirms that the cohesive inter-particle forces, which manifest a linear increment with temperature, are responsible for the fluidization transition.
