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Process for Producing Ultra-High Purity (UHP) Oxygen from an Adsorption-Based Purification System Using Ion Transport Membranes (ITMs) Disclosure Number: IPCOM000031525D
Publication Date: 2004-Sep-28
Document File: 3 page(s) / 31K

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Process for Producing Ultra-High Purity (UHP) Oxygen from an Adsorption-Based Purification System Using Ion Transport Membranes (ITMs)

Oxygen can be recovered from air at high temperatures by passing hot, oxygen-containing gas, preferably air, over non-porous, mixed conducting ceramic membranes.  These membranes, known in the art generically as ion transport membranes (ITMs), utilize an oxygen partial pressure differential across the membrane to cause oxygen ions to migrate through the membrane.

Membranes can be fabricated as tubes or flat plates that are arranged in modules for efficient contact with the hot compressed air.  High-purity oxygen permeate and nitrogen-enriched non-permeate products are withdrawn from the modules.  A comprehensive review of ion transport membranes is given by J. D. Wright and R. J. Copeland in Report No. TDA-GRI-90/0303 prepared for the Gas Research Institute, September 1990. 

A small ITM Oxygen module and associated gas-heating equipment can be used in conjunction with an adsorption-based gas purification system, such as a PSA or VSA, to produce a higher purity oxygen stream.  Integration of the heat and material streams in the combined processes are feasible and possibly advantageous.  In situations requiring small quantities of UHP O2, a unit producing high-purity O2 from a standard PSA or VSA would reduce customers’ bottled-gas inventories and eliminate bottle-handling for high-purity O2.  Alternatively, the unit could be used to fill a cylinder.

PSA or VSA operations for O2 purification typically produce up to about 95% pure oxygen.  Higher purity (typically >99.5%, but as low as 98%) O2 cannot easily be produced from PSA/VSA operations because of the relatively small separation factors characteristic of known adsorbents.  In contrast, ion transport membrane-based systems can have higher separation factors and exhibit near-infinite selectivity for oxygen separation over other compounds.  An ITM-based system combined with a PSA- or VSA-based system can produce high-purity oxygen.  Central to the idea is the use of the medium-purity of the PSA/VSA-produced product as a feedstock to the ITM.  Because oxygen flux through the ITM is an electrochemical process that depends on the ratio of the feed-side to product-side oxygen partial pressure, the re...