ARE THERMALLY COUPLED DISTILLATION-COLUMNS ALWAYS THERMODYNAMICALLY MORE EFFICIENT FOR TERNARY DISTILLATIONS

The thermodynamic efficiency of five ternary distillation configuratio ns to distill ideal saturated liquids into pure product streams are ca lculated and compared. A striking result of this study is that for the fully coupled column (Petlyuk) configuration, which is known to have the lowest heat demand for ternary distillation, the range of values o f feed composition and relative volatilities for which it is the most thermodynamically efficient configuration is quite limited. Among the three thermally coupled column configurations, the side-rectifier and side-stripper configurations tend to provide the most efficient config uration more often than the fully coupled configuration. Generally, th e modified direct and indirect split configurations together provide t he most thermodynamically efficient configuration for more feed compos itions and relative volatilities than do the three thermally coupled c olumn configurations. The high thermodynamic efficiency of these two c onfigurations is primarily due to their ability to either accept or re ject heat at the intermediate temperatures of binary mixtures.