START-UP AND CONTROL OF A DISTILLATION COLUMN USING ADAPTIVE DYNAMIC MATRIX CONTROL - AN EXPERIMENTAL-STUDY

Manual control is conventionally exercised during the start-up of a di stillation column since most linear controllers fail to perform satisf actorily during this highly sensitive transient period. This paper dis cusses the application of an adaptive dynamic matrix control (DMC) sch eme to start-up and control of a pilot scale distillation column. A cl osed-loop on-line identification technique was used to update the DMC controller model to accommodate process-model mismatch. Experimental r esults showed that performance comparable to that obtained with a non- linear model predictive control can be achieved with the present schem e, during both start-up and subsequent single composition control for servo as well as regulatory problems, The adaptive dynamic matrix cont rol (ADMC) algorithm was also extended to multi-input, multi-output sy stems. For a 2 x 2 system, only two of the four partitioned matrices o f the system dynamic matrix could be updated at a time. For the dual c omposition control of a distillation column, the reflux flow was found to have a more profound influence on the column performance as compar ed with the steam pressure to the reboiler. Hence, only the models cor responding to the former were updated. Experimentation on a pilot scal e column showed that adaptive DMC performed better both for regulatory and servo problems, when compared with conventional DMC.