Importance

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Abstract

Disclosed is a method for subjecting feed air to fractionation for recovery of a product oxygen fraction therefrom in a pressure swing adsorption (PSA) process utilizing a nitrogen-selective adsorbent (“NSA”) that is sensitive to water. The PSA process includes the steps of feed pressurization, production, equalization, and blowdown. The improvement to this PSA process commences with placing a bed of pre-treatment adsorbent between feed air and a bed of NSA. Next, a controllable valve is interposed between the pre-treatment adsorbent bed and the NSA bed. Finally, the controllable valve is kept closed during the steps of production, equalization, and when the process is idle. An advantageous NSA is LiX zeolite, Li-LSX zeolite, CaX zeolite, and similar adsorbents, particularly highly hydrophilic zeolites. Another feature of the disclosed PSA cycle is that the pre-treatment adsorbent bed blows-down while the NSA bed equalizes.

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First Claim