Parametric study of the three-bed pressure-vacuum swing adsorption process for high purity O₂ generation from ambient air

A parametric study was carried out to improve the cyclic performance of the three-bed pressure-vacuum swing adsorption (PVSA) process, which consisted of two zeolite 10X beds for equilibrium separation and one carbon molecular sieve (CMS) bed for kinetic separation. Since the adsorption pressure and the feed flow rate of the zeolite 10X bed affected the concentration wave front of each component in the steps of removing impurities in the CMS bed, they played an important role in the final purity and recovery of the air separation. The pertinent step times in the nonisobaric steps, such as the pressurization and the pressure equalization steps of the zeolite 10X bed, contributed to the improvement of both O₂ purity and recovery. In addition, the pressurization and the adsorption steps of the CMS bed served as key steps to purify the oxygenrich feeds from the zeolite 10X bed. The increased pressurization step time leads to an increased adsorption pressure in the CMS bed, and the increased adsorption time implies the prolonged step of removing impurities in terms of kinetic separation in the CMS bed. Therefore, high O ₂ purity with high recovery and productivity could be obtained from the low quality product of the zeolite 10X bed by the increased step times in these two steps. However, increase of these step times might lead to a decrease in final O₂ purity because the breakthrough of impurities occurred through the extended adsorption step time of the zeolite 10X bed. The effect of these step times on the final O₂ purity from the CMS bed was, however, less sensitive than that from the zeolite 10X bed. Furthermore, the recovery and the productivity could be increased simultaneously with a decrease in purity in the variation of pressurization step time. Consequently, O ₂ of 97+% purity with high recovery of 75+% and productivity of 5.8 × 10^-5 cm³/g·s, was produced at a well-tuned operating condition.