Economic Tradeoffs for Extraction Systems

A method for the quick screening of conceptual design alternatives for liquid extraction processes is described. As an example, the extraction of acetic acid from water using diethyl ether as a solvent is considered. First, two feasible extraction flowsheets are generated based on an analysis of the phase behaviour. Design estimates are made using recently developed geometric methods. An economic analysis shows a significant incentive for both flowsheets as an alternative to conventional binary distillation. Using a rank order analysis, it is found that the fractional recovery of solvent is the most important design variables in the extraction flowsheets. Surprisingly, it is found that the more complex flowsheet is the more economically attractive, because it avoids the difficult separation of small amounts of acetic acid from water by distillation.