A fresh look at underwood's method

Document Type

Conference Proceeding

Date of Original Version



Energy consumption in the chemical and petrochemical industries is dominated by distillation. Despite its limitations, Underwood's method remains a widely used tool for determining minimum energy needs in distillation, largely because it is straightforward and gives good results in many situations. A new methodology, the concept of the shortest stripping line, was presented to determine minimum energy requirements for multicomponent separations involving ideal, nonideal, azeotropic, and reactive mixtures. This new methodology can also determine minimum energy consumption for multi-unit processes like hybrid separations (e.g., distillation plus extraction) or reaction/separation/recycle. Underwood's method and its relationship to the concept of shortest stripping lines were studied. In particular, the shortest stripping line approach was further extended to analyze the sensitivities of column composition profiles, and in turn energy requirements, to distillation product compositions. A methodology that combines a robust optimization technique with the shortest stripping line approach was proposed to address the problem of sensitivity of column composition profiles and energy requirements to specified product compositions. This is an abstract of a paper presented at the AIChE Spring National Meeting (Houston, TX 4/22-27/2007).

Publication Title, e.g., Journal

2007 AIChE Spring National Meeting

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