Nonlinear dynamics and control of reactive distillation processes

In some cases reactive distillation is very economical compared to a conventional process design, where reaction and separation are carried out in different processing units. Typical examples are esterification and etherification processes. Consequently, there has been a lot of interest in this type of integrated process during the last years. Emphasis has been on steady state modeling, on development of new processes and on process design. Still, comparably little work has been done on dynamics and control of reactive distillation processes, although these processes can sometimes show an intricate nonlinear dynamic behavior including multiplicities and instabilities. Reliable prediction and understanding of these phenomena is a necessary prerequisite for better process design and control. The objective of this contribution is to give an overview of the present knowledge on dynamics and control of reactive distillation processes with emphasis on the authors work in this field. The outline of the contribution is the following: First, focus is on open loop dynamics of reactive distillation processes involving-multiplicities, self-sustained oscillations and spatio temporal pattern formation also termed as nonlinear wave propagation. Different sources for nonlinear behaviour are systematically identified and implications for process operation and process control are discussed. The second part is concerned with control of continuously operated reactive distillation columns. Emphasis is on inferential control schemes, where the desired product purities are inferred from temperature measurements