Axial Segregation in Bubbling Gas-Fluidized Beds with Gaussian and Lognormal Distributions of Geldart Group B Particles

Bubbling, gas-fluidized bed experiments involving Geldart Group B particles with continuous-size distributions have been carried out. Sand of various widths of Gaussian or lognormal distributions were completely fluidized, then axial concentration profiles were obtained from frozen-bed sectioning. Similar to previous works on binary systems, results show that mean particle diameter decreases with increasing bed height, and that wider Gaussian distributions show increased segregation extents. Surprisingly, however, lognormal distributions exhibit a nonmonotonic segregation trend with respect to distribution widths. In addition, the shape of the local-size distribution is largely preserved with respect to that of the overall distribution. These findings on the nature of local-size distribution provide experimental confirmation of previous results for granular and gas-solid simulations. Lastly, an interesting observation is that although monodisperse Geldart Group D particles cannot he completely fluidized, their presence in lognormal distributions investigated still results in complete fluidization of all particles. (C) 2010 American Institute of Chemical Engineers AIChE J, 56: 3049-3061, 2010