Electrostatic Charging and Entrainment Behaviors of Binary and Quaternary Particulate Systems in Fluidized Beds

A number of commercial fluidization processes involve binary or quaternary particulate systems with different particle sizes and densities. During the operation of multiphase systems such as fluidized beds, electrostatic charges are generated primarily via triboelectric or frictional charging due to the dielectric nature of the materials. The accumulation of electrostatic charge within the system can impact the fluidization behavior and in some cases can be operationally hazardous. In this study, the electrostatic charge generation and accumulation are investigated for binary and quaternary particulate systems using a faraday cup system and an on-line electrostatic probe system. Specifically, the effect of addition of two different fine iron ores (i.e., hematite and magnetite) in fluidized beds is studied in terms of particle-particle interactions and entrainment rates. The behaviors of different particulate systems are found to highly depend on the chemical and physical properties of particles such as size, density, hydrophobicity, surface roughness and even magnetism. The results suggest that the enhanced electrostatic forces between fine and coarse particles due to significant electrostatic charging phenomenon during fluidized bed operation can retain the fines to some extent.