Measurements and Flow Visualization Techniques for Multiphase Systems. Low-Temperature, Wet Coating of Cohesive Particles in a Vortex Chamber Generated High-G Fluidized Bed

De Wilde, Juray [UCL] Eliaers, Philippe [UCL]

The high-G fluidization of particles in vortex chambers allows intensified interphase transfer of mass, momentum and energy and opens perspectives for the low-temperature, wet coating of cohesive particles. The generation of a rotating fluidized bed of such particles requires carefully balancing the centrifugal force and the counteracting radial gas-solid drag force and a careful vortex chamber slot and chimney design. For wet coating applications, the positioning of the nozzle will affect the performance, that is, the coating efficiency. A centrally positioned nozzle inserted via the chimney allows a top/side-sprayed configuration and contributes to minimizing particle losses via the chimney. An experimental study was carried out with a given vortex chamber particle coater design. Combining solids loss measurements, particle size distribution measurements, active component release tests and SEM imaging, the study addresses the effect of the presence of the liquid droplets on the stability of the rotating fluidized bed, the segregation of uncoated and coated particles, the control of agglomeration and the influence of the gas flow rate, the required coating time, the influence of the liquid flow rate and droplet size and the coating efficiency, and the quality of the produced coatings.