Analytical methods are used to compute important operational parameters for an infinite-staged Petlyuk column as a function of the feed composition, feed enthalpy, and relative volatilities. The computational effort is very low, and the methods can be used to quickly evaluate the applicability of a Petlyuk column for a specific separation task. It is found that the largest energy savings of about 40% are obtained when the prefractionator is operated at its preferred split and the feed composition is such that both the upper and lower parts of the main column operate at their respective minimum reflux condition. The position of this boundary region relative to the actual feed is very important when we consider important operational aspects of the column.