Agglomerate Sizes of Binary Nanoparticle Mixtures in a Vibro‐Fluidized Bed

Abstract

Agglomerate size is one of the key factors influencing the fluidization behavior of nanoparticles. The effect of fluidization time, superficial gas velocity, and vibration frequency on agglomerate sizes for different binary mixtures of nanoparticles at the top of the bed was investigated in a vibrated fluidized bed (VFB). The agglomerate sizes decreased and fluidization quality was significantly enhanced owing to introduction of vibration energy. The Richardson-Zaki equation combined with Stokes' law permitted the prediction of mean agglomerate sizes. Experimental and estimated results indicated that vibration led to a smaller agglomerate size. The mean predicted agglomerate sizes were in agreement with those determined experimentally in the VFB.

Agglomerating Vibro-fluidization Behavior of Binary Nanoparticles Mixtures

“…According to our previous report [8], the agglomerate sizes of the three kinds of binary mixtures nanoparticles attain a stable fluidization after about 30 min. Therefore, at a fixed vibration condition (f=40 Hz, A=3.0 mm) and fluidization time of 30 min, the effects of u g on d a of binary mixtures of SiO 2 /TiO 2 , SiO 2 /ZnO and TiO 2 /ZnO nanoparticles are showed in Fig.…”

“…All the experiments were carried out at room temperature and ambient pressure conditions. Similar as our previously paper [8], the same mass ratio binary mixtures of SiO 2 /TiO 2 , SiO 2 /ZnO and TiO 2 /ZnO nanoparticles which have stable agglomerates were taken out carefully from the different axial and radial locations in the top bed while the bed was completely fluidized with a sampling ladle self-made to avoid disruption of their size, structure, and shape. After that, the mixed agglomerate samples were directly analyzed by a positive position metallographic microscope, and then the mean agglomerate size was obtained by taking the arithmetic average of over 50 agglomerates from one sample.…”

“…Different studies showed that agglomerates fluidization of nanoparticles was characterized by a dynamic process governed by the growing of the agglomerates due to cohesive forces and fracturing of the agglomerates caused by breaking forces [1,5,9,10], resulting in the smaller and more stable agglomerates at the top bed, while the larger and looser ones at the bottom bed [8,11]. On this point, the efforts on modeling of the agglomerate size are only meaningful for the top-bed stable agglomerates.…”

“…The Richardson-Zaki (R-Z) equation mainly applied to describe the bed expansion of liquid fluidized beds was also successfully applied to in gas-solid systems [10,12,13], the equation relates the superficial fluid velocity u g with the bed voidag ε which has been analyzed according to mass balance of the binary mixed nanoparticles in the fluidized bed in a previous paper [8], as given by Eq. (1)…”

Population Balance Equation of Cohesive Particle Flow in a Circulating Fluidized Bed

“…Zhou et al [10,11] studied the fluidization of cohesive particles by both experimental investigation and theoretical research. They proposed the probability of agglomerate coalescence or breakup and investigated the flow behavior of agglomerates.…”