Adsorbents for Pressure Swing Adsorption Regeneration

Abstract

Abstract : This work is a continuation of the effort described in Evaluation of Adsorbents for Pressure Swing Adsorption (ERDEC-CR-260). Two significant modifications to the experimental apparatus described in the previous report have been made. A back-pressure regulator has been added to control chemical equilibrator pressure, thus making the feed concentration independent of downstream pressure. A discrete sampling capability has been developed that both confirms continuous concentration measurements and identifies possible chemical reaction products. Based on the results of ERDEC-CR-260, several different types of adsorbents were selected for further analysis. From these experiments, it was determined that the best performing adsorbents were silica gels. Experiments were then conducted using Silica Gel 40, Silica Gel 70A, Silica Gel 250A, and Silica Gel 500A to determine the affect of particle size and pore diameter on regeneration rate. Particle size effects were examined using two different mesh cuts of Silica Gel 40, and results clearly indicate that using smaller particles dramatically increases regeneration rates. All four silica gel samples were used to conduct the pore diameter study. A definite, near linear, relationship was found between pore size and clean-up rate. For example, the clean-up rate for Silica Gel 500A was twice that for Silica Gel 250A. The major conclusion drawn from this work is that the larger pore diameter silica gel adsorbents (250A and 500A) are the best materials for the feed-end layer in a PSA bed.