No abstract

The steady−state operation of a continuous industrial fluidized-bed granulator for urea production with multiple growth and cooling beds in series is modeled. The model is based on mass and energy balances, which account for the behavior of all the phases that coexist within the unit, as well as the bed hydrodynamics patterns. The granules growth that occurs through the deposition of droplets on urea seeds, followed by water evaporation and solidification of the urea present in the solution, is taken into account by considering the concentrated nature of the inlet urea solution. The proposed mathematical model successfully predicts industrial data for different plant capacities. The total urea dissolution heat is the most important thermal effect involved in the growth chambers. The granulator operation provides significant heat and mass transfer within the unit, with the water evaporation being almost complete and the outlet gas and particle temperatures being very similar.