Rapid pressure swing adsorption is commonly used in the design of portable oxygen concentrators, which serve as a viable alternative to oxygen cylinders in the medical field. Rapid pressure swing adsorption processes present challenges in process design that slower PSA processes do not possess. These mainly deal with how to efficiently operate a PSA process on a small scale while dealing with an increase in mass and heat transfer resistance caused by higher gas velocities. This study illustrates how to deal with these challenges through the design of a rapid PVSA process using a rate enhanced adsorbent that provides a high purity product (97% oxygen using argon free air) and extremely favorable recoveries (50-60% at pressure ratios between 4-5) with a BSF under 100 lbs. /TPD oxygen.
Using a commercial Li-X zeolite, a lab-scale two column PVSA system was used to design a process utilizing rapid PVSA. The design included first examining the effect of cycle time on the oxygen recovery at a range of pressure ratios (varying from 2.5-7 by changing the desorption pressure). The adsorption/desorption pressure, amount of gas used for the feed and purge steps, and product purity were maintained as the cycle time was reduced. This provided a method in which any change in oxygen recovery was almost solely assessed to the reduction in cycle time and not variations in other process parameters. Additionally, a range of adsorption pressures were examined to determine an ideal operating range using rapid PVSA for this adsorbent.
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