An investigation of the interactions between system characteristics and controllability for reactive distillation systems

Abstract

Reactive distillation is an emerging process intensification technology, although its operation and control are complex due to the interactions between reaction and separation within the column. In this work, the impact of reaction and separation, as well as design parameters, on the controllability of reactive distillation processes is investigated, using a systematic methodology developed. Case studies of industrial interest are considered, varying in the key (reaction, separation and design) parameters, in order to investigate the relative impact of the latter on the controllability of the reactive distillation systems. It is shown that the system with slower kinetics demonstrates an increased difficulty in rejecting feed disturbances for both one point (V-only) and two-point (LV) control configurations. Even when linear model predictive control (MPC) is considered based on a state-space representation of the model, the system with slower reaction kinetics is still more difficult to control, for both set point change and load disturbance. It is also shown that revision of the optimal steady state design variables, such as the total number of stages, may be beneficial for the controllability of the process. The importance of maintaining feed ratio in stoichiometric processes is identified and discussed, as failure to do so may result in failure to maintain both product purities when two point control is considered.