Two-compartment modeling and dynamics of top-sprayed fluidized bed granulator

A top Spray Fluidized Bed Granulator (SFBG) is being modeled and analyzed with the help of population balance equation (PBE) and analytical as well as numerical results. The mathematical model for SFBG is derived using the concept of compartment modeling. The granulator is divided into two compartments, a wet compartment in which aggregation is the dominant process, and a dry compartment that is dominated by breakage. A new discretization is given to solve the model which is based on the idea of conserving the important properties of the system. The numerical results of the moments derived by the new discretization are validated against the developed exact results for different combinations of the aggregation and breakage kernels. The model is also tested for physical tractable kernel and the numerical results are authenticated with the results of constant volume Monte Carlo. The two-compartment model is shown to behave dynamically in a distinctly different manner to the simpler one-compartment model. The most critical parameter is the exchange flow between the compartments. When the characteristic time for this flow is low relative to the rates of aggregation and breakage, the effect of breakage is amplified disproportionally relative to breakage, and whereas the single-compartment granulator always reaches steady state between the rates of aggregation and breakage, the two-compartment model may, under some conditions, lead to continuously decreasing size under the dominance of breakage.