Conference Dates

May 1-5, 2011


In this work, the effects of gas permeation through flat membranes on the hydrodynamics in a pseudo-2D membrane-assisted gas-solid fluidized bed have been investigated experimentally. A combination of the non-invasive Particle Image Velocimetry (PIV) and Digital Image Analysis (DIA) was employed to simultaneously investigate emulsion phase and bubble phase properties in great detail. Counter-intuitively, addition of secondary gas via the membranes, that constituted the confining walls of a gas-solid suspension at conditions close to incipient fluidization, did not result in a larger, but in a smaller bubble diameter, while gas extraction on the other hand, resulted in a larger equivalent bubble diameter, although in this case the effect was less pronounced. This could be explained by changes in the larger scale particle circulation patterns due to gas extraction and addition via the membranes: gas extraction leads to densely packed zones near the membranes, forcing bubbles through the center of the bed, where they become elongated and increase in size. Gas addition, on the other hand, totally inverts the particle circulation compared to a fluidized bed without membranes, splitting up bubbles in the center and forcing them towards the membranes, thus decreasing the bubble size.