Adopting feed splitting in design of reactive distillation columns with two reactive sections

For the separations of reacting mixtures featuring the heaviest and lightest reactants and intermediate products, although feeding the heaviest/lightest reactant to condenser/reboiler of reactive distillation columns with two reactive sections (RDCs-TRS) at top/bottom favors the reaction operation involved, it poses a detrimental effect to the separation operation involved because the reactants tend to move through the stage for withdrawing the intermediate product and increase consequently separation difficulties. A performance index is derived for the RDC-TRS and feed splitting is adopted to suppress the drawback. The separations of an ideal quaternary reaction, the esterification of lactic acid with methanol, and the esterification of palmitic acid with isopropanol, are employed to evaluate the proposed design philosophy. The resultant design is found considerably superior to the RDC-TRS and exhibits better or at least comparable performance with the reactive distillation column with a top-bottom external recycle. These outcomes indicate that feed splitting is especially effective for enhancing internal mass and energy integration between the reaction operation and separation operation involved. Despite the existence of adverse internal energy integration in case of reactions with thermal effect, the reinforced internal mass integration could still facilitate the resultant design a potentially competitive alternative.