On the controllability of middle-vessel continuous distillation columns

Controllability issues for conventional and middle-vessel continuous distillation columns are addressed in this paper by using different controllability and resiliency measures. It is shown that, by using a middle-vessel continuous column (MVCC), the sensitivity of the control system performance to the direction of input disturbances can be significantly reduced with respect to a conventional column, in such a way that effective composition control can be achieved with simple proportional-integral controllers even for highly ill-conditioned columns. The tuning of composition loops in an MVCC is shown to be easier than that in a conventional column.