| Article ID | Journal | Published Year | Pages | File Type |
|---|---|---|---|---|
| 154512 | Chemical Engineering Science | 2016 | 9 Pages |
•A new “slope curve method” for the conceptual design of extraction columns is described.•The method easily finds all feasible product compositions.•Only LLE data needed as input.•Limitations by internal pinches can be quickly identified.
A new method for the conceptual design of counter-current extraction columns, the slope curve method (SCM), is presented. It is a graphical method based on the equilibrium stage model and developed here for ternary mixtures. The well-known stage-to-stage construction in the ternary phase diagram is replaced by a concise representation in the so-called slope diagram. In that diagram, the slope curve represents the tie lines and operating lines represent material balances. Infinite column height is assumed so that for given feed and solvent composition, the only remaining degree of freedom is the solvent-to-feed ratio. Varying that parameter, all feasible solutions are obtained in the slope diagram. The corresponding product compositions can be reconstructed. Using the method, it is readily shown that internal pinches only occur for certain classes of mixtures, which can be readily identified based on an analysis of the shape of the slope curve. As the SCM yields a complete survey of all feasible solutions it is particularly suited for feasibility studies in conceptual design as well as for obtaining general insights in extractive separations.
