MINIMUM REFLUX BEHAVIOR OF COMPLEX DISTILLATION-COLUMNS

A continuum model for multicomponent distillation in the minimum reflux limit, first proposed by K. Nandakumar and R. P. Andres, is refined for the special case of constant relative volatility (CRV) and constant molar overflow (CMO) and is extended to columns with multiple feeds and multiple products. A relaxation algorithm for calculating steady-state conditions in any minimum reflux CRV, CMO column is established. This generalization of Underwood's classic treatment of single-feed columns is used to explore the characteristics of several single-feed and multiple-feed distillation systems. Critical operating points at which the steady-state composition profile in a minimum reflux column is indeterminate are identified and analytical expressions predicting the location of these points are established.