Pressure
drop data have been
collected and analyzed
to give the umf values of
0.01 and 0.39 cm/s for
SiO2 and Al2O3 powders
respectively. These
values are relatively
high, about several
orders of magnitude
higher than the umf of
primary nanoparticles, in
spite of the application
of an acoustic field. With
regards to the bed
expansion curves it can
be noted that both the
powders showed some bed expansion even for superficial velocities lower than the
respective umf. In addition, both the materials showed a homogeneous fluidization
like Geldart’s Group A powders.