Two-Stage Vacuum Pressure Swing Adsorption Using AgLiLSX Zeolite for Producing 99.5+% Oxygen from Air

Abstract

Oxygen concentrations above 99.5% are required for several applications, mainly in the medical and aerospacefields. Two-stage pressure swing adsorption (PSA) processes, combining kinetic separation with equilibrium separation, havebeen developed for producing 99+% oxygen from air. Argon and nitrogen are kinetically removed from the air feed using acarbon molecular sieve adsorbent and the remaining nitrogen is removed using a N2/O2 selective zeolite. Despite that, two-stageprocesses are often unattractive, complex, and energy consuming, requiring two or more compressors/vacuum pumps. Moreover,most of the two-stage units described in literature are unable to reach the required oxygen purity of 99.5%. This work studiesthree energy-efficient two-stage vaccuum PSA (VPSA) processes, combining an equilibrium based PSA (EPSA) or a kinetic basedPSA (KPSA) for the first stage, with a VPSA unit packed with the Ar/O2 selective zeolite AgLiLSX for the second stage, aimingto produce 99.5+% oxygen; the use of zeolite AgLiLSX allows removing argon besides nitrogen. The best two-stage VPSAconfiguration allowed obtaining a 99.8% oxygen stream at 6% of recovery and a 99.5+% oxygen stream at 14+% of recovery.