Control strategies for alternative configurations in continuous industrial granulation processes

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

Sheffield

Workshop; International Granulation Workshop; 2015

Sheffield University

This paper focuses on enhancing the operation of industrial granulation circuits via the designand performance evaluation of different control strategies. Particularly, control strategies wereimplemented on a urea-granulation flowsheet simulator based on an alternative circuit configurationrespect to the often used (Uhde fluidized-bed granulation technology, UFT). The proposedconfiguration is based on a simulator of the UFT circuit which has been previously developed andvalidated by our group in a gPROMS modeling environment (Process System Enterprise). This newconfiguration includes a bypass of fines coming out of the crusher (flowrate and size of the seedsfed back to the granulator), the granulator discharge, the fluidization air temperature and flowrate,and the gap between the crusher rolls as potential manipulated variables. In order to maintain theoperation within the desired limits, it is necessary to control the granulator top vacuum pressure, thefluidized bed levels and temperatures, and the mean size and span of the product size distribution.Through sensitivity analysis and/or the Relative Gain Array criterion, the optimal pairing betweenmanipulated and controlled variables was first determined. Subsequently, the proposed controllerswere tuned following an optimization-based method (integral of time absolute error, ITAE). All thestudied control loops were effective to either eliminate disturbances in the granulation circuitvariables or to reach new set-points for the controlled variables. Summarizing, this contributionprovides granulation process engineers with useful control strategies for solving typical transientoperational challenges.