Distillation operations are major consumers of energy, by some estimates comprising forty percent of the energy usage in the refining and chemicals industry. Obtaining the maximum energy efficiency from this unit operation is obviously very important. For many distillation columns there is a tradeoff in operation between energy usage and product recovery and setting the proper usage target involves a calculation of the economic tradeoff between these two factors. However, distillation is a non-linear process and normal economic valuations add more non-linearities to the economic objective functions. In addition, the normal product quality variability observed leads to requirements for statistical evaluation. Hence, calculation of the correct target can be complicated. In this paper, these non-linear economic effects are reviewed and techniques to calculate the correct usage targets presented.

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