Study On The Performance Of A New Compact Type 4-Bed Pressure Swing Adsorption Adsorber For Oxygen Manufacture From Air

A new compact type 4-bed pressure swing adsorption (PSA) apparatus wasconstructed. Each bed is a round slice with diameter 88 (o.d.)×10 and depth 10 mm.The four slice beds are stacked one above the other by airproofed flanges. Theperformance of the new type PSA equipment was tested on air separation producingoxygen. Zeolite 5A was used for adsorbent and a six-step operation process wasplanned: adsorption, pressure equalization, countercurrent blowdown, countercurrentpurge; pressure equalization and re-pressurization. To determine an appropriateoperation condition, breakthrough curves were collected on the setup under a constantpressure (0.6 MPa) for different feed flowrates (110.58 Sccm,163.62 Sccm,216.66Sccm,269.70 Sccm,322.74 Sccm,375.78 Sccm and 428.82 Sccm) as well as undera constant feed flowrate (216.66 Sccm) for different operation pressures (0.3MPa,0.4MPa,0.5MPa,0.6MPa,0.7MPa and 0.8MPa). It was found the optimal operationpressure is 0.6MPa and the optimal feed flowrate is 269.70 Sccm with respect to theconcentration and recovery of oxygen. Further experiments were carried out onstudying the factors affecting the purity and recovery of oxygen. The first factor is theenvironmental temperature. It was shown that environmental temperature exerts agreat effect on oxygen purity and recovery as well as productivity and energy cost;therefore, the time span of each operation step was determined at 18.5℃ of roomtemperature. The optimal time spectrum determined is: 5 s for pressure equalization,30 s for blowdown, 6 s for purge with purging ratio (P/F) 0.1. The time span ofre-pressurization is related to the adsorption time and must follow certain rules. It wasexperimentally proven that the optimal time span needed for each step did not changewith the direction of pressure equalization, but pressure equalization at the exit endsyielded better result than at the entrance ends. The effect of pressure and time span ofadsorption on the purity and recovery of oxygen as well as on productivity and energycost was studied at 18.5℃ with pressure equalization at the exit ends. It gave resultsof oxygen purity in 40%～70%,recovery in 15%～30%,and energy cost in 0.862～1.97kwh/(Nm3 O2) with productivity of 28.78～56.55 NL(O2)/[h, kg(adsorbent)]. Itis concluded from the study that the new compact type multi-bed adsorber is feasiblefor PSA operation. It provided a design possibility for a small but efficientoxygen-producing machine, which may have important implication for fuel celldriven vehicles, health care and military purpose.