Agglomeration behavior of the dense medium in a gas-solid separation fluidized bed

In this study, the atomic force microscopy (AFM) was used to measure the micro-forces between different par-ticles and study the influence of different operating parameters on the formation of particle clusters in the gas-solid fluidized bed separation process. In this way, the mechanism of liquid bridge formation and fracture can be elucidated, thereby providing a theoretical basis for inhibiting the formation of particle clusters. The results indicated that for relative humidity (RH) < 40%, the extrusion liquid bridge is the dominant factor for the formation of the particle liquid bridge, and the liquid film thickness, h, and liquid film volume, Vsq, vary linearly with RH; however, once the RH is > 40%, these relationships become nonlinear. The adhesion force between magnetite powder particles was found to be the largest and that between pulverized coal particles was found to be the smallest, with the mixture of the two particle types being in between. Further, the adhesion between particles increased monotonically with RH, while showing a maximum value with increasing particle separation. A theoretical analysis of the critical fracture distance, D*rupture, of the particle liquid bridge showed that, as the liquid bridge volume, V*, and contact angle, theta, increase, D*rupture gradually increases, but its rate of increase rate. The theoretical analysis was found to be largely consistent with the experimental data, only deviating at low RH.

Automated summary

This study used atomic force microscopy (AFM) to measure micro-forces between particles and investigate the impact of different operational parameters on the formation of particle clusters in gas-solid fluidized bed separation process. The findings help understand the mechanism of liquid bridge formation and fracture, providing a theoretical basis to prevent particle cluster formation. Results indicate that the extrusion liquid bridge is the main factor for particle liquid bridge formation when relative humidity (RH) is less than 40%, while the relationships between liquid film thickness (h), liquid film volume (Vsq), and RH are linear. However, these relationships become nonlinear when RH is greater than 40%.