Fluidized-bedmeltgranulation: Coating andagglomerationkinetics andgrowth regime prediction

MARTA VILLA; BERTIN, DIEGO; COTABARREN, IVANA; PIÑA, JULIANA; VERONICA BUCALA

POWDER TECHNOLOGY

ELSEVIER SCIENCE SA

Lugar: Amsterdam; Año: 2016 vol. 300 p. 61 - 72

0032-5910

Mass and population balance equations are used to describe the spray-on melt granulation process in a batch fluidized bedwhere coating and agglomeration can occur simultaneously. Two different models are considered to describe the agglomerationkinetics: the Equipartition Kinetic Energy (EKE) and Size Independent (SI) kernels, while the coating kinetics isrepresented by a power law. Based on experimental data obtained under different operating conditions (melt and air atomizationflowrates, air fluidization velocity, seed diameter and bed temperature), the coating and agglomeration kineticparameters are fitted to correctly predict the final particle size distributions. It is concluded that the SI kernel and the zeroordercoating kinetics best describe the agglomeration and coating mechanisms, respectively. A correlation to predict theSI kernel from macroscopic variables and properties of the system is proposed. This tool can be used to provide startingkernel factors for solving the PBEs governing spray-on melt granulation in fluidized-bed granulators. Finally, a criterionto predict the limit of agglomeration occurrence is formulated. The criterion, which is developed in terms of dimensionlessnumbers that depend on process conditions and take into account mass, heat and momentum transfer phenomena, isfound to be appropriate to predict the growth regime for fluidized-bed spray-on melt granulation of urea (i.e., the specificstudied system).