(131c) Point Efficiency Data for Distillation Column Design at Elevated Liquid Viscosities

Liquid viscosity is considered to be one of the most important physical properties that influences distillation column efficiency. Although most of the distillation efficiency correlations that have been published thus far emphasize the importance of viscosity, they were developed or validated based on efficiency data at liquid viscosities less than 1 cP. For example, the O’Connell correlation was developed based on efficiency data at less than 0.5 cP. However, distillation with liquid viscosities greater than 1 cP is encountered in certain cases in the chemical process industry. Examples include separation of monomers from polymeric solutions, vacuum distillation of viscous crude oil, separations involving ionic liquids, and vacuum distillation of bio-oils to obtain biofuels. Therefore, distillation efficiency data at liquid viscosities greater than 1 cP are required to accurately quantify the effect of liquid viscosity on distillation efficiency and to develop improved efficiency correlations.

In scale-up of distillation column design, point efficiency is the foundation upon which tray and column efficiencies are calculated. Oldershaw columns have been proven to be effective in representing the point efficiency of commercial columns. In this paper, point efficiency data collected using an Oldershaw column for 4 different test systems, including a new viscous test system (cyclopentanol/cyclohexanol) that we recently established¹, at liquid viscosities ranging from 0.2 to 4.2 cP will be presented. The methodology used for quantifying the effect of liquid viscosity on point efficiency will also be presented. These new data will be useful in the design of distillation columns operating at elevated liquid viscosities.

1. Manivannan, R. G.; Mohammad, S.; McCarley, K.; Cai, T.; Aichele, C., A New Test System for Distillation Efficiency Experiments at Elevated Liquid Viscosities: Vapor–Liquid Equilibrium and Liquid Viscosity Data for Cyclopentanol + Cyclohexanol. Journal of Chemical & Engineering Data 2019, 64, (2), 696-705.