Predicting Multiple Steady States in Equilibrium Reactive Distillation

Abstract

This paper presents graphical methods for the prediction of output multiplicities caused by the reactive vapor-liquid equilibrium in equilibrium reactive distillation. The methods rest upon the limiting case of reactive columns with infinite length operated at infinite internal flows (∞/∞ analysis) and are directly applicable to systems where the reactions take place in the entire column (“non-hybrid” columns). Applying a necessary and sufficient condition for the existence of output multiplicities, the region of all feed locations leading to multiple steady states can be constructed. Since many industrial reactive systems are “hybrid” (non-reactive columns with a reactive core), the prediction methods are extended to cover hybrid columns where analogous results can be obtained as for non-hybrid systems. The methods will be applied to the well-known MTBE reactive distillation process and the physical phenomena which cause multiplicities in this process are determined by analytical investigations and compared to the available literature results.