The V
min diagram is introduced to effectively visualize how the minimum energy consumption
is related to the feed-component distribution for all possible operating points in a two-product
distillation column with a multicomponent feed. The classical Underwood equations are used to
derive analytical expressions for the ideal case with constant relative volatility and constant
molar flows. However, the diagram can also be used for nonideal mixtures. The V
min diagram is
very insightful for assessing multicomponent separation in a single column and is even more
powerful for complex column arrangements, such as Petlyuk columns (parts 2 and 3 of this
series of papers).