Rapid pressure swing adsorption for reduction of bed size factor of a medical oxygen concentrator

Reduction of the adsorber size of a medical oxygen concentrator (MOC) employing a generic pressure swing adsorption (PSA) technology is an ongoing research and development activity. The MOC typically produces a 90-93% O ₂-enriched product gas from ambient air at a rate of ≤10 L/minute (LPM) for individual use. A common practice is to reduce the total cycle time (t_c, seconds) of the PSA process in order to decrease the bed size factor [BSF, pounds of adsorbent in the PSA unit per ton of contained O ₂ per day production rate (TPD_c)]. Adsorbent columns packed with very small adsorbent particles are used to enhance the adsorption kinetics for rapid PSA cycle operation. An experimental mini-PSA set up was used to measure the performance of a simulated Skarstrom-like PSA cycle using a commercial sample of LiX zeolite as the air separation sorbent. Different adsorbent particle sizes, adsorption pressures, and cycle times were tested. It was experimentally demonstrated that BSF cannot be indefinitely reduced by lowering t_c because of finite adsorbate mass transfer and gas-solid heat transfer resistances, as well as column pressure drop during the desorption step. A BSF of ∼25-50 lbs/TPD_c with an O₂ recovery of ∼25-35% for production of ∼90% O₂ could be achieved by the PSA process using a dry, CO₂-free air feed at a pressure of 3-4 atm, an adsorbent particle size of ∼0.35 mm, and a total cycle time of 3-5 s. A novel snap on concept of a truly compact and portable MOC was proposed.