Process Design and Control of Reactive Distillation in Recycle Systems

This chapter focuses on the design and control of reactive distillation (RD) columns, which are seen as an integral part of an intensified chemical process. While most of the published literature presents analyses of the RD columns as standalone process units, this work frames the RD columns within a process where recycle streams (to these columns) are present, as typical to industrial practice. These recycle streams originate from the incomplete conversion of reactants or their conversion to undesired by-products. Therefore, the unreacted reactants need to be recovered and recycled, while the by-products need to be recovered and reconverted into reactants followed by their recycle to the RD columns. A case study of industrial importance is used to illustrate key aspects of design and control of such reactive distillation systems with recycles. The design is focused on developing the topology of the entire process and solving the mass and energy balance based on which key process performance indicators (e.g. reactant utilization, energy efficiency, material and energy intensity, and carbon dioxide emissions) can be analyzed. The control is focused on developing a plantwide strategy to achieve the material inventory (in other words, balancing the reactions’ stoichiometry), along with achieving the desired production rate and product purity. Several key process changes (e.g. flowrate and composition changes) are implemented to test the proposed control structure of the plant. All this work makes use of both steady-state and dynamic, rigorous process simulations.