NONLINEAR OBSERVERS FOR DISTILLATION-COLUMNS

A full-order nonlinear observer for distillation columns is presented. Temperatures are measured at different points of the column and compared to the observer's output temperatures. The error is weighed by a spatially distributed function. The resulting term is used to correct the mathematical model of the observer. The estimated temperature and concentration profiles are then given by the state of the observer. The mathematical model used includes material balances on each tray as well as thermodynamic state-functions. It consists of dynamic and algebraic equations, exhibits severe nonlinearities and is of high order. Physical insight is used to design the observer. The movement of the regions of high mass transfer rate determines the essential dynamic quality of a column. Knowing the location of these mass transfer regions allows observer design and positioning of measurement points. The obtained observer was successfully tested in several simulation studies. It exhibits dynamic behaviour and robustness properties.