Study of fluidization transition from Geldart B to A induced by high
temperature using electrical capacitance tomography
Abstract
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.