Fluidization of solids with CO2 at pressures from ambient to supercritical

Beds of two granular materials belonging to groups A-B and B of the Geldart classification of powders were fluidized by carbon dioxide at 35 degrees C and at 1 to 80 bar. Within this pressure interval, spanning from subcritic al to supercritical conditions, the fluid density changes from the values t ypical of dilute gases to those of liquids. The hydrodynamic behavior of th e bed changes accordingly. The bed behavior was investigated by visual insp ection of the bed and by analysis of the time series of the pressure drop a cross the bed and of the heat-transfer coefficient between the bed and a ho t wire probe. The boundaries between different captive fluidization regimes -incipient fluidization, onset of bubbling, and the incipient and fully est ablished turbulent regime - were mapped in gas superficial velocity us. flu id density phase planes for the two granular materials investigated.