Evaluation of control schemes of a binary distillation column.

Abstract

Utilizing experimental transient data, of a ten-plate pilot plant binary distillation column, reported by Gerster and co-workers (26), various control schemes were investigated by means of analog computer simulations for a 10% step disturbance in feed composition. Employing reflux manipulation to maintain constant overhead product composition, the optimal location of the sensing element was determined. The utility of Rosenbrock's optimum control point policy was also considered. The so-called two-point control exhibits strong interaction between the two control loops. For close control of the overhead product composition, feedforward plus feedback compensation control was found very effective in decreasing the maximum deviation of the controlled variable from the desired value and reducing the time required for the controlled variable to return to its original steady state value.