(248c) Multi-Stage Agglomerate Structure and Solids Mixing Behavior of Nano-Particle in Fluidized Bed

The fluidization of nano-particles can make nano-particle processing and handling much more efficient. Many nano-particle systems can be fluidized in the form of agglomerates. The determination of agglomerate parameters like agglomerate density and diameter is very important in the research of nano-particle fluidization. And solids mixing behavior is crucial to nano-agglomerate fluidized bed Reactor (NAFBR). In the first part of this study, Mercury Intrusion Porosimetry (MIP) was used to determine the pore distribution of a kind of nano SiO2 powder R972 from Degussa and hence the average agglomerate density and diameter. The agglomerate density is 2~3 times the bulk density of these nano-powders. In the second part of this study, the solids mixing behavior in a fluidized bed with the fluidized material R972 from Degussa was investigated. The axial and radial solids dispersion coefficients in this system are two orders of magnitude lower than those in traditional fluidized catalytic cracking catalyst systems. The axial solids dispersion coefficients increase with the increasing of superficial gas velocities and range between 9.1*10^-4 m²/s and 2.6*10^-3 m²/s. There is a step between the solids dispersion coefficients in the particulate fluidization domain and those in the bubbling and turbulent fluidization domain. As superficial gas velocities step up, the radial solids dispersion coefficients increase gradually, whose values are from 1.2*10^-4 m²/s to 4.5*10^-3 m²/s.