Aerated silo discharge of fine pharmaceutical powders

Aeration was successfully assessed as a flow promotion technique in the silo discharge of three fine pharmaceutical powders with different flowability. Air injection was effective to overcome arching and piping phenomena due to cohesion of all the tested powders and turned out to be effective in tuning the solid flow rate for an easy flowing powder. A maximum solid discharge rate was obtained for a critical air flow rate able to fluidize the powder bed during the discharge. Model predictions of the solid discharge rate as a function of the air flow rate are in good agreement with experiments provided a reasonable estimate of the aggregate size is available.