(84d) Packed Column Hydraulics and Continuous Phase Transitions

In spite of extensive efforts over the years aimed at understanding how the hydraulics of packed columns operated countercurrently depend on the geometrical characteristics of the packing, the physical properties of the liquid and vapor phases and the vapor/liquid loadings within the packed section, no public domain model or correlation has proved completely adequate for column rating or design. With this in mind we explore the hypothesis that the flooding locus in packed columns operated in countercurrent fashion represents an envelope of second order phase transitions from vapor to liquid continuous operation. We show that an appropriate renormalization of vapor and liquid loads to an incipient flood point at constant liquid load results in a collapse of column pressure drop data onto a single ?master? curve for a great many packings (see the example below). The flood points determined in this way are well-described by the Wallis equation. Further, we show that the scaling arguments can be used to generalize and extend these results to systems with physical properties other than those of the original experimental system.

The reduced data can be fit to any of a number of correlating expressions. Finally we will show that model predictions compare extremely well with experimental data across a broad spectrum of packing styles and distillation systems without the need for any type of ad-hoc correction factors.