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 extracti on of acetic acid from water using diethyl ether as a solvent is consi dered. First, two feasible extraction flowsheets are generated based o n an analysis of the phase behaviour. Design estimates are made using recently developed geometric methods. An economic analysis shows a sig nificant incentive for both flowsheets as an alternative to convention al binary distillation. Using a rank order analysis, it is found that the fractional recovery of solvent is the most important design variab les in the extraction flowsheets. Surprisingly, it is found that the m ore complex flowsheet is the more economically attractive, because it avoids the difficult separation of small amounts of acetic acid from w ater by distillation.