Self-Tuning and Conventional Control of an Industrial Scale Packed Distillation Column

The performance of self-tuning and a variety of conventional control strategies are examined when applied to the overhead product composition control of a packed distillation column. These control strategies are tested under various sets of conditions on a packed distillation column situated B.P. Chemicals, South Wales, U.K. Conventional PID control action is employed throughout-being considered the most likely type of control action for this application. The controller parameters were estimated using three different closed loop response tuning criteria for discrete controllers, viz. those due to Yuwana and Seborg (YS), Jutan and Rodriguez (YS-JR) and Wardle and Heathcock (YS-WH). An additional criterion (YS-JR-decrease gain) is proposed in the present work and is found to give better control than YS-JR method in a number of cases. The best conventional PID action is compared with self-tuning PID control. The success of the various control actions are estimated using an integral square of the error (ISE) criterion and it is shown that self-tuning PID control provides better control than conventional PID action for the cases studied.