Process Alternatives for Coupling Reaction and Distillation

Areactive distillation column combines reaction with distillation, and is known to be advantageous for some reaction systems, but not for others. Sometimes it is a breakthrough technology, yet in others a reactive distillation column does not give pure products, and is therefore infeasible. For cases where a reactive distillation column is not feasible, it is useful to determine alternatives with combined reaction and distillation that rely on conventional distillation systems to give pure products. The advantage of such alternatives is the use of simultaneous reaction and distillation to improve the yields and/or selectivities to products, and also that they require smaller recycle flows. Many alternatives can be generated with a potential advantage over the conventional process of reaction followed by distillation. During the conceptual design stage of a process it is vital to decide quickly whether reactive distillation is likely to be a good process concept. We describe an approach that first determines feasible product splits for single-feed continuous reactive distillation. For chemistries where one or more products cannot be obtained as a pure product stream from the column, the geometric method of attainable regions is used to determine the feasible products and alternatives using simultaneous reaction and distillation. These alternatives are then combined with conventional separation systems to get pure products. Using systematic methods, a large number of flowsheets are generated, which are then evaluated for feasibility using rules, heuristics and mass balances.