Fluid-bed melt granulation: growth regime prediction

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

Sheffield

Workshop; 7th International Granulation Workshop; 2015

Sheffield University

Fluid-bed granulators usually present operating problems due to competitionbetween different growth mechanisms (agglomeration and/or coating). Therefore, it isimportant to develop tools for predicting the main or dominating size enlargementmechanism for a wide range of operating conditions.From experimental data available for urea melt granulation in a bottom-spray fluidbedsystem, the feasibility of using dimensionless numbers already proposed in the openliterature to predict the growth mechanism was first studied. Even though the Stokesand Flux numbers have been reported to be successful in predicting the dominantgrowth mechanism for other granulation systems, both were of limited applicability tourea melt granulation. Thereby, for the urea granulation process, a new dimensionlesssemi-empirical parameter was postulated in order to predict the occurrence ofagglomeration in terms of granulator operating variables. The developed approachallowed successfully predicting the formation of agglomerates for a wide range ofoperating conditions. Consequently, the proposed parameter is of practical utility todetermine the compensation that could be implemented in a given operating variable,against a change in another one, in order to ensure the desired growth mechanism.