Microscale Two-Phase Flow Structure in a Modified Gas-Solid Fluidized Bed

Transient signals were registered in a modified fluidized bed and statistically analyzed. Particle agglomerates in the emulsion were identified from signals and the agglomerate properties were investigated. The volume fraction of the bubble phase varied from 0.16 to 0.52 with operation pattern and spatial positions. Mean solid holdup and its standard deviation inside bubbles significantly increased when operation pattern transitioned from bubbling fluidization to turbulent fluidization, while the increasing tendency leveled off in the turbulent regime. The volume fraction of particle agglomerates in the emulsion decreased with increasing superficial gas velocity, varying over the range of 0.2-0.65 with flow regimes. Agglomerate solid holdup slightly fluctuated in the range of 0.608-0.63, barely influenced by switch of operation pattern. Agglomerate frequency varied over the range of 1.5-3.7 Hz and the duration time was <0.3 s for most cases. The correlations of agglomerate volume fraction and frequency were proposed. The terminal velocity and the size of the effective agglomerates in the emulsion phase were calculated via a modified Richardson-Zaki equation and found to be 4.16 m/s and 1.19 mm, respectively.