Hardware selection and design aspects for reactive distillation columns. A case study on synthesis of TAME

Abstract

We have carried out a step-by-step design study of a reactive distillation (RD) column for synthesis of tertiary-amyl ether (TAME) in order to investigate the influence of the choice of hardware on column design. Two different types of internals are compared: active Raschig rings and catalytic bales. Firstly, an equilibrium (EQ) stage model is used to obtain conceptual column design parameters. Detailed mass transfer and pressure drop calculations are then carried out to determine the column diameter and heights of the reactive and non-reactive sections of the RD column. Active Raschig rings have superior mass transfer characteristics but poorer pressure drop characteristics as compared to catalytic bales and therefore yield shorter and fatter column configurations. The detailed hardware configuration is finally checked with a rigorous nonequilibrium (NEQ) stage model to ensure that the designs are adequate and to investigate scope for further improvement. Our study underlines the importance of using NEQ models for column design and optimization. EQ stage models provide only initial estimates of column designs. The chosen column configurations must be carefully checked with rigorous NEQ models. Furthermore, our study reveals that the amount of catalyst used in the reactive section needs to be carefully chosen; excess of catalyst could lead to promotion of the reverse reaction of TAME to the reactants.