Effect of Changes in Operating Variables on Stage-wise and Cumulative Separation in Binary Multistage Distillation

Abstract

Abstract The progressive separation that occurs stage-wise within a multistage distillation column is characterized by the cumulative extent of separation, ζ N ; while the contribution of individual stages, δ N , to the overall separation is given by the difference between ζ N for successive stages. These indexes permit the “goodness” of separation for individual stages and for the entire column to be compared on an equivalent basis. This paper examines the effects of changing operating variables of reflux ratio, feed rate, feed composition, and feed stage location on the separation obtained in a distillation column containing a fixed number of ideal stages, and how the single-stage contribution changes when these variables are altered from the design value. The calculations show that the reflux ratio (R) is probably the most important variable in determining how well a column makes a separation. Separation declines rapidly as R is reduced below the design value, as the feed rate is increased at constant ...