An improved model for determining fractal structure of nano-agglomerates

Effects of operating conditions on fractal structures of three nanoparticle agglomerates (SiO2, TiO2, and ZnO) in a vibro-fluidized bed were investigated. An improved model is proposed by combining the fractal relation, Richardson-Zaki equation, and mass balance. This model was used to predict substantial properties of nanoparticle agglomerates, such as fractal dimension and size of the agglomerate particulate fluidization. It was shown that with increasing vibration intensity, the fractal dimension of agglomerates decreases slightly, while the number of primary particles in the agglomerate decreases significantly. It was found that the fractal dimension of nanoparticle agglomerates is in the range of 2.63-2.78, and the number of primary particles in the agglomerate is in the order of 10(10). Agglomerate size reaches a constant value at high vibration frequency. Calculation results indicated that the vibration frequency has a more important role than its amplitude in reducing agglomerate size. Minimum fluidization velocity was calculated by applying estimated agglomerate sizes, and it was found that the results were in close agreement with the experimental data.