Pressure-swing adsorption using layered adsorbent beds with different adsorption properties:: I -: Results of process simulation

A simulation study was conducted on layered-bed pressure-swing adsorption, PSA, processes with adsorbents that differ in their adsorption properties. As an example, an oxygen, O-2, vacuum-swing adsorption, VSA, process was analyzed to investigate relationships between process performance and adsorption properties of the adsorbents used. For two adsorbents with identical nitrogen-to-oxygen, N-2/O-2, selectivity but different N-2 and O-2 capacities, placing the high-capacity adsorbent at the product end and the low-capacity adsorbent at the feed end of the adsorption bed gives a better performance than the case of reversing layering of these adsorbents. However, for two adsorbents with different values of N-2/O-2 selectivity but identical N-2 capacity, changing the bed-layer configuration does not show a significant difference in O-2-VSA performance. The advantages of layering a high-capacity adsorbent on product end of the bed are demonstrated by an examination of the N-2-loading difference in a VSA cycle. The modeling study also reveals an effect of cycle features (e.g., equalization step) on the effectiveness of using layered-bed configurations in VSA/PSA processes. It suggests that layering appropriately two adsorbents with different adsorption properties could result in better VSA/PSA-process performance than using a single-layer bed with either of the two adsorbents.