Impact of disturbance magnitudes and directions on the dynamic behavior of a generic reactive distillation

The dynamic behavior for a high-purity/high-conversion reactive distillation is investigated. The impact of disturbance magnitudes and directions on both open loop and closed loop stability of the system is studied. Excess of less volatile reactant in two-reactant-two-product generic reactive distillation is found to enhance open loop stability, but decreases the products purity. However, excess of more volatile reactant trigger the system to another steady-state. Open loop changes in the manipulated variables (i.e. vapor boilup from the reboiler and reflux rate from the condenser) in certain directions are found to be intolerable due to their effect on both the reaction kinetics and the fractionation capacity of the column. The performance of the open loop system is improved significantly with the inclusion of internal inventory control of one of the reactants but this has been found to be insufficient when there is a change in some inputs in certain directions. Steady-state rating analysis on the system suggests that the limitations on certain inputs could be resolved by including a single-end controller, which will act to maintain the separation capacity of the column and thus stabilizes the system.