Dynamic Optimization of a Urea Granulation Circuit

COTABARREN, IVANA; BERTIN, DIEGO; BUCALÁ, VERÓNICA; PIÑA, JULIANA

Lausanne

Workshop; 5th International Granulation Workshop; 2011

Particles Product Group-University of Sheffield

In this work, a dynamic model of a complete urea granulation circuit (developed in previous contributions) is used to perform dynamic optimizations, being the main goal the maximization of the plant capacity. The circuit flowsheet includes mathematical models for a fluidized bed granulator, a cooling unit, double-deck vibrating screens and double-roll crushers; the last two models were validated against industrial data. Particularly, in this contribution the fluidization air flowrate used in the core unit of the circuit (the granulator) is automatically fixed according to the pressure drop of the granulator beds reflecting commonly industrial air flows set ups. Several dynamic optimizations cases were developed in order to maximize plant capacity over time. For each case, different combinations of possible control variables were tested (i.e., urea melt flowrate, granulator fluidization air temperature, granulator discharge area). For all the performed optimizations, physically realistic operating constraints were considered. The results provided new promising operating points that can be achieved by tracking the calculated optimal time-trajectories of the selected control variables. Besides, the main circuit bottlenecks for increasing the throughput were identified.