Study on the feasibility of split crossing distillation compartment boundary

This paper proposes a graphical method for analyzing the feasibility of splits crossing distillation compartment boundaries. In this method, the univolatility curve, which reflects the inflexions of residue curves, and the volatility order diagram, are employed. The analysis shows that, for ternary system with one binary minimum azeotrope, splits can only cross the distillation compartment boundary in one direction. For a given feed composition, the feasible product compositions lie in a small region bounded by two straight lines: one passes through the stable (or unstable) node and feed point; the other is the transition line passing through the feed point and tangential to the feed residue curve. Aspen Plus simulation is used to check the feasibility of splits and product composition regions. The results are in good agreement with the analysis. The proposed method is simpler than the existing residue curve map based tools but does effectively predict feasibility with the same efficiency. It can only apply to ternary mixtures at present.