Impact of material property and operating conditions on mass flux profiles of monodisperse and polydisperse Group B particles in a CFB riser

Experiments directed at understanding local mass flux behavior of Geldart Group B materials in the riser of a gas-solids circulating fluidized bed (CFB) have been carried out. Three monodisperse materials (with differences in particle size and/or material density), two binary mixtures (one with only a particle size difference between the species and the other with only a material density difference), and one continuous particle size distribution (PSD) have been investigated at four operating conditions. Results show that the riser axial position has the greatest influence on mass flux behavior, especially near the top of the riser, where profile shapes consistently have an inverted U-shape or V-shape. The material type (i.e., monodisperse materials of different particle sizes and/or particle densities or different types of polydispersity) and operating conditions effects are secondary but more apparent at the riser bottom. An interesting observation involving binary mixtures is that while the mass flux profiles of the density-difference binary mixture mimics that of one of its (monodisperse) constituent components, the size-difference binary mimics neither of its two monodisperse components.

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► Experimental mass flux behavior of six materials throughout the riser.
► Three monodisperse, two binary mixtures and one continuous size distribution.
► Riser local position is the key influence of mass flux for all materials.
► Operating condition and material type effects are secondary.
► Behavioral differences among materials highlight the role of polydispersity.