Powders belonging to group A of the Geldart classification have been studied in
detail using the bed collapse technique. To obtain the correct properties of the powders a
model is developed, which takes into account the system configuration for both one and twovalve
experiments. An experimental apparatus has been assembled and used to validate the
model using glass balloting in the size range 22-106 µm. The system allows simultaneous
measurements of total bed height, using a digital camera, and pressure transients at various
positions along the vertical axis. The powders have been sieved to obtain 6 size ranges and
the fluidization properties have been measured, Mixtures of particles have been prepared and
the effect of the size differences has been investigated.