Identification of thermal zones and population balance modelling of fluidized bed spray granulation

Air temperature measurements in a fluidized bed of glass beads top sprayed with water showed that conditions for particles growth were fulfilled only in the cold wetting zone under the nozzle which size and shape depended on operating conditions (liquid spray rate, nozzle air pressure, air temperature, and particles load). Evolution of the particle size distribution during agglomeration was modelled using population balance and representing the fluidized bed as two perfectly mixed reactors exchanging particles with particle growth only in the one corresponding to the wetting zone. The model was applied to the agglomeration of non-soluble glass beads and soluble maltodextrin particles spraying respectively an acacia gum solution (binder) and water. Among the three adjustable parameters, identified from experimental particle size distributions evolution during glass beads agglomeration, only one describing the kinetics of the size distribution evolution depended on process variables. The model allowed satisfying simulation of the evolution of the particle size distribution during maltodextrin agglomeration.

Graphical AbstractAir temperature measurements in a fluidized bed of glass beads top sprayed with water showed that conditions for particles growth were fulfilled only in the cold wetting-active zone under the nozzle which size and shape depended on operating conditions. Evolution of the particle size distribution during non-soluble glass beads and soluble maltodextrin particles agglomeration was modelled using population balance with two perfectly mixed reactors exchanging particles. The agglomeration kernel βi,j was defined with three parameters identified from agglomeration trials with glass beads and maltodextrin particles. Only the agglomeration rate β0 was found to depend on process variables.Figure optionsDownload full-size imageDownload as PowerPoint slide