Air separation by a small-scale two-bed medical O-2 pressure swing adsorption

A small-scale two-bed six-step pressure swing adsorption (PSA) process usin g zeolite 13X was performed to provide oxygen-enriched air in the medical s ystem. The binary mixture N-2/O-2 (79/ 21 vol %) was used for PSA experimen ts. Cyclic behaviors of the PSA process were investigated from unsteady- to steady-state conditions. Also, effects of various operating parameters on the PSA performance such as the P/F ratio, adsorption pressure, feed flow r ate, and adsorption step time were investigated experimentally under the no nisothermal condition. The effect of the P/F ratio was noticeably changed a ccording to the adsorption pressure and feed flow rate conditions. The high er the adsorption pressure, the slower the increasing rate of purity and th e higher the decreasing rate of recovery. However, as the adsorption pressu re became higher, the effect of the P/F ratio on the O-2 purity became smal ler. Furthermore, the effect of adsorption pressure on the O-2 purity and r ecovery was diminished gradually to the increase of the P/F ratio. The feed flow rate also had a strong effect on the O-2 purity. As for the product p urity, the low feed flow rate began to lose its advantage with an increase in the P/F ratio. The recovery and productivity at a high feed flow rate wa s higher than those at a low feed rate even under the high product purity r egion. The dominant operating factor to determine the O-2 Purity was change d from the adsorption pressure to the feed flow rate as the P/F ratio was c hanged from low to high values. The modified linear driving force (LDF) mod el similar to a solid-diffusion model predicted the transition behavior of the cyclic process better than the LDF model.