MODELING ON AGGLOMERATE PARTICULATE FLUIDIZATION OF NANO-PARTICLES: Determination of Agglomerates Size and Internal Structure

摘要

Nanoparticles in gas fluidization are found in form of agglomerates. These nanoparticle agglomerates consists of sub-agglomerates that are highly porous with chainlike structures. The overall porosity of fluidized nanoparticle agglomerates can be as high as 98%. In this study, an analytical model is developed to calculate the flow partitions through and around the porous agglomerates, as well as the drag force on an agglomerate of nanoparticles in a swarm of other similar agglomerates. Our analysis shows that the drag forces of nanoparticle agglomerates can be approximated as those of solid spheres with the same diameter and equivalent density, with an error margin up to 20% for the nanoparticles used in this study. Based on this approximation and the Richardson-Zaki equation, an analytical method is further proposed to estimate the size and minimum fluidization velocities of nanoparticles agglomerate in the agglomerate particulate fluidization (APF). The predicted size and minimum fluidization velocities of APF nanoparticles agree fairly well with our experimental results.