Fluidization is used extensively in industry for drying, mixing and agglomeration processes for applications that range from gasification of biomass, ion exchange processes and high efficiency carbon capture. Although their applications are broad and there are many studies on fluidized beds there is not a lot of information on the initial stages of fluidization when it is induced by local fluid injection. The experiments presented in this talk deal with the study of these early stages of fluidization at the center of a cohesionless bed using the techniques of Planar Laser Induced Fluorescence (PLIF) and refractive-index matching.
The experimental setup allowed for several parameters to be systematically studied, including particles sizes from 3mm to 10mm, initial bed heights up to 250mm, and different diameters for the injection port from 10mm to 40 mm. Furthermore some experiments varying the particle density and surface roughness of the particles were conducted. The effect of each of these variables on the flowrate needed for fluidization, the magnitude of the velocities at certain regions of the bed, and the dimensions for the fluidization zone are some of the results that will be presented in this talk. It is confirmed in these experiments that the critical flow rate is primarily dependent on the initial height of the granular bed. However, contrary to what was observed previously for relatively small bed height, this dependence is not a linear relation but a progressive saturation was found for larger heights. Conversely, the shape of the chimney seems related only slightly to the bed height and significantly more to the diameter of the injection port but remains far from being proportional. These quantitative data can provide more insight in the behavior of fluidization improving our understanding of the phenomena.