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Processing costs comparison

Q: Is there a template for comparing the processing costs of extraction versus distillation with rectification? Optima is a contract manufacturer with two Karr Columns. We would like to point out the advantages of liquid extraction to our customers. With energy costs rising, I would think there are advantages even if both unit operations work.

A:

Your question is clearly a good one with energy prices at their current levels. However, I am not aware of a template which compares solvent extraction economics with distillation alone. Liquid extraction is often used to exchange a difficult distillation with an easier distillation. Companies are currently evaluating the application of liquid extraction to reduce energy consumption. Unfortunately, comparative economics will vary from plant to plant. Solvent selection must be carefully evaluated and is not trivial. In the U.S., the economics will likely be compared with an existing distillation system which is already paid for. The savings in operating cost must justify any new capital. In some cases, the existing distillation system maybe utilized for solvent recovery. In this best case, the new capital would involve an extraction column, stripper to recover solvent from the raffinate and the solvent inventory within the extraction loop. In summary, I am not aware of a template that compares the economics of a solvent extraction system (extraction with solvent recovery) with a distillation system. In regards to an existing plant, the economics must be evaluated on the unique characteristics associated with each plant.