Fluidization of fine powders with air in the particulate and the bubbling regions

Several fractions of a silica—alumina catalyst and an impregnated catalyst were fluidized with air to check published bubble point correlations and to determine the expansion of the dense phase in the bubbling region. The minimum bubbling velocities were fairly close to those reported by Geldart and others, but U_mb varied with only the 0.6 power of the particle size. The dense phase expansion was significant even at velocities much above U_mb and corresponded to relative velocities up to 2 – 3 times U_mf.