Analysis of the product granulometry, temperature and mass flow of an industrial multichamber fluidized bed urea granulator

Abstract

In this work, a complete dynamic model of a continuous industrial fluidized bed granulator for urea production is presented. Three growth and three cooling chambers in series are simulated. Mass, energy and momentum balances are solved for all the fluidized beds together with the population balance equation (PBE). Since each granulator chamber can be modelled as a continuous stirred tank (CST), the multichamber granulator is represented by a series of CSTs. Applying the developed model, the open-loop behaviour of the product granulometry is particularly investigated. With this aim, and to further develop efficient control strategies, different step disturbances are assayed. Based on the results of the performed sensitivity study, it can be concluded that the log-normal distribution function gives an appropriate description of the PSD in each chamber, the granulometry response times control the dynamics of the complete granulation circuit, the seeds' PSD is the variable that most affect the outlet particle size distribution, and that mild recycle ratio values are adequate to stabilize the granulator operation.