Design and economic trade‐offs of extractive crystallization processes

A systematic procedure is formulated for the separation of a binary mixture by means of extractive crystallization. It shous that two flowsheet structures can handle systems with a wide variety of solid‐liquid phase behaviors, including components with simple eutectics, multiple eutectics, and compound formation. Design equations are presented for both flowsheet structures. In addition, design variables and constraints are identified. The economic trade‐offs in extractive crystallization processes are examined through the analysis of an example: the complete separation of paraxylene from meta‐xylene using n‐pentane as the extractive solvent. Comparison of our general methodology with the system‐specific designs reported in the literature shows that the latter are process alternatives of the former.