Mass transfer in shallow aerated vibrated powder beds

Abstract

Mass transfer rates are reported for granular beds (depths = 24 and 1 mm) aerated by upward flow of nitrogen both in absence of vibration and also subjected to vibration at intensities affording maximum accelerations = two and four times gravity. Nitrogen flows were both below and above minimum gas-fluidizing velocities in absence of vibration. At both 24- and 1-mm bed depths, vibration at intensity four times gravity can enhance mass transfer by a factor between about 1.4 and 2. For mass transfer, bed depth is an important variable, with or without vibration. Without vibration, mass transfer at 1-mm depth can be ∼ 10 to 15 times greater than transfer in a 24-mm bed. A correlation is available that deals successfully with influence of bed depth in our data, both with and without vibration. Data reported herein at 1-mm depth bear upon performance of a chemical microreactor with cross-flow of gaseous reactants through particles in the coherent-expanded (CE) vibrated-bed state. The data suggest that a mass-transfer limitation need not ordinarily be taken into account in analysis of microreactor kinetic data for a chemical reaction for which a fluid bed reactor is an appropriate commercial choice.