Formulation of a model for packed distillation columns on the basis of field tests

Abstract

On the basis of a series of field tests which were made on a packed distillation column located near Refugio, Texas, several possible methods for the modeling of packed distillation columns were investigated. Because of the serious limitations of Murphree-type efficiencies as well as mass transfer rate expressions for the description of mass transfer in a distillation column in the process of separating multi-component mixtures, the possibility of the use of models employing these quantities was rejected. On the other hand, it is shown herein and elsewhere that the vaporization efficiencies are non-zero, finite, and positive numbers even though the corresponding Murphree efficiencies and overall mass transfer coefficients are either negative, zero, or undefined. Thus, the concept of a mass transfer section or vaporization efficiency was used in the modeling of a packed distillation column. Several methods for the use of vaporization efficiencies in the modeling of packed distillation columns are presented. These methods were tested by the use of the data obtained from field tests. Several of these methods appeared to be about equally satisfactory for the modeling of a packed distillation column. Of these various methods, the one most strongly recommended possessed the desirable characteristic that it provided a procedure for the averaging of the E[subscript ji]'s over all runs as well as a means for testing the accuracy of the correlation.