Reduced models and control of distillation columns with sharp temperature profiles

The dynamic behaviour of distillation columns with sharp temperature profiles is investigated by simulation using a full set of balance equations, The simulation results lead to considerably simplified dynamic models which are applied in the design of the control systems. Two examples are presented: A state observer and an optimal control have been employed in the control of a large-scale extractive distillation column. The control algorithm was programmed into a ??-processor and was implemented in a large-scale plant at HOECHST-AG (Frankfurt). The system has proved its high reliability and efficiency in extensive field tests and in two years of continuous operation. A state observer and a KALMAN-filter is used to estimate the state variables and unknown feed disturbance of a distillation column with a vapour side stream. These estimated values are fed to an optimal state feedback with disturbance variable compensation. Simulation results show that this control system ensures the product specifications, even if large disturbances occur.