(380e) Impact of Process Design On Dynamic Controllability of a Generic Reactive Distillation Column

The role of process design on steady-state multiplicity and dynamic controllability is studied for a generic ideal reactive distillation column. The effects of number of reactive trays, number of separation trays, and column operating pressure are explored to quantify the impact of design variables on the effectiveness of an inferential two-temperature control structure.

The steady-state input-output relations of the optimum steady-state design indicate the severity of input multiplicities because of the nonlinear nature of the reactive distillation columns. It is demonstrated that this severity of input multiplicity is decreased when more reactive trays are added to the column. The results also show that using a secondary sensitive tray in the reactive zone instead of the most sensitive tray in the rectifying section avoids inverse response. Thus, a wider range of disturbances can be handled using the same inferential two-temperature control structure. In addition, enhancing the number of separation trays helps to process operation and contribute to controllability. On the other hand, the results indicate that the changes in operating pressure do not provide any improvement in controllability.

Although the results obtained in this work are closely dependent on a specific process, a generalized conclusion can be derived for the development of reactive distillation columns. This paper demonstrates that there may be trade-offs between optimum steady-state design and dynamic controllability. It indicates that using sub-optimum designs could be necessary to decrease the severity of input multiplicity, and increase the operability region of the control structure.