Dynamics and control of high purity heat integrated distillation columns

The dynamic behaviors of a high purity internal thermally coupled distillation column (ITCDIC) are studied. It is observed that these dynamic behaviors are characterized by high sensitivity to disturbances, strong asymmetric nonlinearity, and a distinct inverse response, which all cause an increased mismatch between the linear model and the real plant. Investigation on the interaction between overhead and bottom composition loops indicates that a high purity ITCDIC is an ill-conditioned system with a gain directionality problem. Internal model control (IMC) and multiloop proportional, integral, and derivative (PID) control are explored in this study. Modified IMC and multivariable PID control with singular value decomposition are also presented to further the improvement of control performance and guarantee smooth operation of the high purity ITCDIC.