Synthesis and Design of Reactive Distillation Columns

During the past decades, reactive distillation has received intensive attentiondue to the well known benefits of integrating distillation with reaction in a singleunit. Significant capital savings, improved conversion and selectivity, avoidanceof azeotropes, together with heat integration are some of the main advantagesof using reactive distillation. Many applications have proven to be economicallyadvantageous by using reactive distillation (e.g. MTBE and TAME synthesis,production of methyl-acetate, manufacture of di-isopropyl-ether, oligomerisationof linear butenes and others). Whereas there are many procedures available forthe synthesis of non-reactive columns or reactive-separation systems, thesynthesis of reactive distillation columns is still a challenge, due to thecomplexity and the high number of design parameters involved. Availableconceptual design methods generally address three (or four) components andfully reactive columns, but there is still a lack of systematic conceptual designmethods for more general column configurations and for multi-componentsystems.The aim of this work is to develop a methodology to identify promising columnconfigurations and to obtain column design parameters (number of reactive andnon-reactive stages, reflux and reboil ratios, feed condition) for a given feedmixture and a set of desired products. A new systematic design method forreactive systems reaching equilibrium allows the analysis of the impact ofdifferent configurations (fully reactive or hybrid columns) and feed policies(single- or double-feed columns) on column performance. The methodology isextended to account for kinetically-controlled reactions in synthesis and designof reactive distillation columns. Systems with two degrees of freedom(according to the Gibbs phase rule) were considered for equilibrium reactions,and ternary and quaternary systems for kinetically-controlled reactions.Reactive distillation column designs generated by the methodology are presented as illustrative examples. Their predicted performances are shown tobe in good agreement with those predicted by rigorous simulation usingHYSYS.The approach can easily be automated and typically generates multipledesigns, allowing a design engineer to efficiently compare various designoptions including hybrid and fully reactive columns, single- and double-feedconfigurations, and different sets of operating parameters for a given columnconfiguration. The new methodology developed in this work facilitates a stepchange in conceptual design practice, offering a systematic and easy to use toolfor the synthesis and design of reactive distillation columns.