A previous article (Hwang, 1991) presented a nonlinear wave theory for predicting the dynamic behavior of binary distillation columns, in particular the severely nonlinear behavior of columns producing high-purity products. Viewing the movement of the composition and temperature profiles in a distillation column as the propagation of nonlinear waves, this theory provides a simple mathematical model for distillation dynamics and a cause-and-effect analysis of nonlinear phenomena such as high steady-state gains, large response lags, strong dependence on disturbances, and asymmetric dynamics. The article also elucidated the inevitable link between nonlinear behavior and high-purity operation with a discussion of two mechanisms for the material transport from one column end to the other. Recently, Han and Park (1993) applied the nonlinear wave model to a profile-position control strategy for a high-purity column and showed very encouraging results.This article fortifies the nonlinear wave theory by including the dissipation effect at column ends as well as feed and product side streams and nonuniform flow rates. In particular, the column-end effect is so critical to countercurrent processes as

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