PAIRING AND LOOP TUNING OF A TRAY DISTILLATION COLUMN
RAWIA S. HASSAN *
Faculty of Graduate Studies and Scientific Research, Karay University, Sudan
MAHASIN B. ELYAS
Faculty of Graduate Studies and Scientific Research, Karay University, Sudan
GURASHI A. GASMELSEED
Department of Chemical Engineering, Faculty of Engineering, University of Science and Technology, Sudan
*Author to whom correspondence should be addressed.
Abstract
A control strategy was developed to determine the appropriate control loops that let the column to operate at steady state without flooding, weeping and entrainment. The aim is to operate the column with the required top and bottom compositions. From the control strategy, block diagrams were constructed and the transfer functions were identified. From these block diagrams the overall transfer functions were calculated and the characteristic equations were obtained, both for closed and open loops. The characteristic equations were then used for stability analysis, tuning, offset investigation and response simulation. As these multi-loops are interactive, pairings for the controlled and manipulated variables were determined using relative gain array (RGA) and the loops were coupled according to the magnitude of the interaction indexes.
Keywords: Tuning, pairing, stability analysis, relative gain array