A Parametric Reactive Distillation Study: Economic Feasibility and Design Heuristics

The integration of reaction and distillation into a single column is called reactive distillation or catalytic distillation. Reactive distillation provides many benefits such as reduced capital and operating costs, circumventing non-reactive azeotropes, and overcoming equilibrium limited reactions. Industry has been successful in applying reactive distillation; however the integration of reaction and distillation is not applicable for all reaction/separation systems and it is not always clear when reactive distillation is a feasible design alternative.

Heuristics or rules-of-thumb are an integral part of process systems engineering and are used to provide initial guidance and insight for the analysis of process feasibility and conceptual design. Heuristics are developed from experience, computer simulations, and process data and usually are simple rules that greatly reduce the effort required to determine initial process feasibility and design. Due to the complex interactions that occur when combining reaction with distillation, heuristics for reactive distillation have been slow to develop.

In order to generate a set of heuristics for single column reactive distillation, a parametric study was conducted for ideal chemical reactive systems involving one or two reactants and one or two products. Each reactive system was divided into regions of similar component boiling point ordering which were expected to exhibit similar reactive distillation characteristics. The parametric study focused on the affects that changing relative volatility and chemical reaction equilibrium have on reactive distillation. Simulation results were used to develop a set of heuristics which outline the initial reactive distillation column design required to produce a desired product as well as the limits of economic feasibility. The generation of these heuristics was facilitated by a graphical representation which relates economic feasibility to reaction equilibrium constant, volatility ordering, relative volatility, and reflux ratio. The graphical representations are a useful screening tool which can be used to identify systems likely to benefit from single column reactive distillation. These heuristics were verified using real chemical reactive systems that are available in the reactive distillation literature.