Control schemes of internal thermally coupled distillation columns for non-ideal mixtures

The control problem of a non-ideal internal thermally coupled distillation column is studied. An effective control scheme is one key to apply this energy-saving distillation column in practical chemical industry. The investigation analyzed difference between non-ideal and ideal systems firstly. Three control strategies, namely, predictive PID control (P-PID), robust PID control (R-PID) and conventional PID control (D-PID), were designed and applied to the process. The ethanol-water system is adopted for illustrative example. Three different control methods were evaluated and compared with respect to both servo and regulatory control performance. The results demonstrate that all methods work well for set point transfer of both overhead and bottom products and various external disturbances. P-PID is the best one. It achieves the quicker respond speed and the smaller remaining error than two others.