Clustering behavior of solid particles in gas-liquid-solid circulating fluidized beds studied by telecentric photography

Abstract

The clustering behavior of solid particles in the riser of a gas-liquid-solid circulating fluidized bed significantly affects phase mixing, mass and heat transfer characteristics, but little work has been carried out on this topic. To fill this knowledge gap, we used an invasive telecentric photography to measure and investigate the axial and radial distributions of cluster characteristics of solid particles in the riser of the three-phase circulating fluidized bed. The results showed that at present experimental conditions, cluster size followed a log-normal distribution in the riser. Within the ranges of superficial gas, liquid and particle velocity of 5.6 × 10⁻³ to 11.2 × 10⁻³ m/s, 112 × 10⁻³ to 162 × 10⁻³ m/s, and 0.85 × 10⁻³ to 2 × 10⁻³ m/s (or auxiliary liquid velocity 20 × 10⁻³ to 50 × 10⁻³ m/s), respectively, 90 % of clusters consisted of about 2 solid particles, with sizes ranging from 0.7 mm to 1.2 mm. Cluster size and velocity increased with superficial liquid velocity, but they were less affected by superficial gas velocity and exhibited a radial structure. Particle aggregation by shedding vortices leads to the cluster formation.