The paper addresses the transition to the bubbling regime of solid beds belonging to Geldart's group A, from ambient temperature to 500°C. The analysis of the influence exerted by operating temperature on the variables that characterize both the homogeneous expansion of the bed and the onset of a steady bubbling regime is conducted on the fluidization map of the fluidized bed, namely the voidage-velocity diagram into which results of the fluidization and bed collapse experiments are merged. The results obtained show that at elevated temperatures the ability of the fluidized bed to preserve the homogeneous fluidization regime is extended to unusually high voidage levels. Even past the appearance of a steady bubble flow, the dense phase voidage exhibits a residual dependence on interparticle forces induced by high temperature.
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