Reaction Hysteresis: A New Cause of Output Multiplicity in Reactive Distillation

Jacobsen and Skogestad (1991) described two causes of multiple steady states in binary distillation via an analysis of the fundamental equations of the equilibrium stage model for distillation processes. Later, Bekiaris and Morari (1993) described multiple steady states in azeotropic distillation using a geometric analysis based on the conditions of perfect fractionation (infinite number of stages and infinite reflux ratio). Commercial process simulators (Pro/IITM and Speed UpTM) were used to investigate multiple steady states in reactive distillation via the construction of bifurcation diagrams (the locus of solutions obtained by varying a single continuation parameter). These results indicate that the mechanisms described by Jacobsen and Skogestad (1991) and Bekiaris and Morari (1993) are each pertinent to reactive distillation processes. However, some examples of multiple steady states cannot be adequately explained with the available explanations and a fourth cause of output multiplicity, applicable only to hybrid reactive distillation, was proposed. Supplementary simulation studies indicate that the proposed explanation is sound.