Vapor split manipulation in extractive divided-wall distillation columns

Several alternative process equipment configurations have recently been proposed to replace the conventional two-column extractive distillation process. One interesting configuration features a single column with a divided wall running from the stripping section all the way two the top of the column. There is only one reboiler at the base of the column, but each of the segregated upper sections has its own independent condenser, reflux and distillate product. The vapor split at the bottom of the wall is fixed at design by the location of the wall. Steady-state economic advantages are claimed over the conventional two-column process. However, the dynamic controllability of this process is in question because the loss of the ability to manipulate the vapor split reduces the number of control degrees of freedom. The purpose of this paper is to propose a new control structure that avoids this loss of control flexibility by manipulating the pressures on the two sides of the wall.