Investigating Control Schemes for an Ideal Thermally Coupled Distillation Column (ITCDIC)

The control schemes of an ITCDIC are addressed. A modified IMC scheme (M-IMC) is proposed to overcome model/plant mismatch of the Internal Model Control scheme (IMC). Predictive PID control (P-PID) and Adaptive Predictive control (AP-PID) schemes are also presented to improve effectively the response speed of the multi-loop PID control (M-PID) and eliminate its residual error. A detailed comparative investigation on the above five control schemes was performed. Simulation results demonstrate all the schemes are able to keep two end products within their specifications. M-IMC is the best one with the fastest response speed. AP-PID is the second choice since it is better at dealing with sudden set-point transitions and complex external disturbances than P-PID. M-PID cannot compete with AP-PID and P-PID due to its slow servo response speed and large residual error. IMC ranks last as it is extremely sensitive to changes in the operating conditions.