A graphical method for designing reactive distillation columns II. The McCabe-Thiele method

Abstract

This paper shows how to construct a McCabe-Thiele diagram for binary reactive distillation. We consider two types of reaction that are consistent with binary mixtures: isomerization (R1 <-> P1) and decomposition (R1 <-> 2P1). We can account for reaction by tracking only two features of the diagram while constructing it. First, the intersection point of the operating line with the y = x line can be called the reactive cascade difference point, and it moves in a manner directly determined by the ratio of the molar extent of reaction (or reaction turnover flowrate) to the product flowrate. Second, the heat supplied (removed) by reaction decreases (increases) the slope of the operating line while not changing the location of the reactive cascade difference point. By tracking these two features, one can quickly sketch such a diagram. We also show how to construct a McCabe-Thiele diagram if the reaction zone is only at the feed stage. Finally, we discuss a case in which the reactive cascade difference point moves past the feed composition and the bottom product composition is less pure than the feed composition.