GAIN SCHEDULING FOR COMPOSITION CONTROL OF DISTILLATION COLUMNS

Composition control loops for high purity distillation columns are highly non-linear, particularly their gain characteristics. A simple gain scheduling approach suggested by Shinskey is evaluated. This approach involves a linear approximation to the process gain when product purity increases and the assumption of constant gain when purity drops. Total loop gain is kept constant when purity increases. Digital simulations show that gain scheduling yields significant improvements in control performance.