Performance Assessment of Different Control Structures for Generic Reactive Distillation Using Linear and Nonlinear Process Models

This paper compares the closed-loop performance of three control structures using an approximate linear model to that when a rigorous nonlinear process model is used for a generic reactive distillation. It is shown that an approximate linear model behaves essentially similarly to a nonlinear model in a closed-loop system when the deviation of process variables resulting from the disturbance is within the region of the base steady state. Responses based on the linear model for various control structures show a good agreement when compared to those based on the nonlinear model under the same conditions. It is found that the linear process model could be used to develop a robust control system when the control valves are conservatively designed. However, it becomes inadequate if the system is open-loop pseudostable or unstable. The performance of the linear model is shown to be better in a single-end control system than in a dual-end control system because of the nonlinearity effect, which is more pronounced in the latter.