Air separation unit (ASU) has become a process integral to many other processes mainly because of the significance of its constituents in many industrial applications. Eminent among them are nitrogen, oxygen and argon. New combination air separation processes for oxygen production are developed that use an uncommon adsorption unit, Mutual Pressure-Swing Adsorption (MPSA) [also known as feed purge pressure swing adsorption], to increment the oxygen concentration of the feed to the cryogenic distillation plant. Two cases are studied: 1-MPSA before the main air compressor increases oxygen concentrations. 2-MPSA after the main air compressor increases oxygen concentrations to significantly higher values. The goal of this work is to assign demonstration of concept for combination air separation processes, based on our findings to optimize the units.