Air separation by a small-scale two-bed medical O2 pressure swing adsorption

A small-scale two-bed six-step pressure swing adsorption (PSA) process using zeolite 13X was performed to provide oxygen-enriched air in the medical system. The binary mixture N-2/O-2 (79/ 21 vol %) was used for PSA experiments. 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 rate, and adsorption step time were investigated experimentally under the nonisothermal condition. The effect of the P/F ratio was noticeably changed according to the adsorption pressure and feed flow rate conditions. The higher the adsorption pressure, the slower the increasing rate of purity and the higher the decreasing rate of recovery. However, as the adsorption pressure became higher, the effect of the P/F ratio on the O-2 purity became smaller. Furthermore, the effect of adsorption pressure on the O-2 purity and recovery 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 purity, 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 was higher than those at a low feed rate even under the high product purity region. The dominant operating factor to determine the O-2 Purity was changed from the adsorption pressure to the feed flow rate as the P/F ratio was changed from low to high values. The modified linear driving force (LDF) model similar to a solid-diffusion model predicted the transition behavior of the cyclic process better than the LDF model.