The oxygen purity produced by pressure swing adsorption (PSA) processes is limited to 95%, with the rest being essentially argon. This oxygen grade is suitable for many industrial applications. However, medical applications, cylinder filling, oxyfuel cutting in metal fabrications, and fuel cells technology with recirculation loop, among others, require oxygen with a higher purity (99% or above). In this paper, a study of high-purity oxygen production by a PSA unit using a silver exchanged zeolite from Air Products and Chemicals, Inc., with oxygen/argon adsorption selectivity is presented. This study comprehends the determination of adsorption equilibrium isotherms of oxygen, nitrogen, and argon as well as the simulation and optimization of a PSA experimental unit and the corresponding experimental validation.

A dynamic model of small valveless pressure swing adsorption (PSA) and vacuum and pressure swing adsorption (VPSA) units for the production of oxygen was developed for the purpose of simulation and optimization. This valveless operation, very often used in commercial units, results in a more complex cycle than the classic Skarstrom cycle, differing in the optimization conclusions and presenting specificities that cannot be ignored in the modeling and simulation. Three different commercially available adsorbents were evaluated for use in these units: Oxysiv 5 and Oxysiv 7 from UOP and SYLOBEAD MS S 624 from Grace Davison. The units' performances (product recovery and power consumption) using each adsorbent were compared for cycles with the same pressure ratio. The simulation results were found to be in agreement with experimental results obtained on a commercial unit.

A dynamic model, a simulator, and an optimization procedure were developed for small oxygen pressure swing adsorption units with different equalization configurations, top-to-top equalization (TE), bottom-to-bottom equalization (BE), and cross equalization (CE), and three different commercial adsorbents, Oxysiv 5 and Oxysiv 7 from UOP and Sylobead MS S 624 from Grace Davison. These units' cycles have the peculiarity of having the pressure history dependent on the product flow rate, which makes them more difficult to simulate and optimize than the classic Skarstrom cycle. The units' performances (product recovery and power consumption) using each adsorbent and equalization type were compared for cycles with the same pressure ratio. The simulation results were shown to be in agreement with the experimental data obtained with Oxymat 3, an oxygen concentrator from Weinmann. The optimization procedure lead to an improvement of the unit's performance.

A multiresolution adaptive approach for the solution of two-dimensional partial differential equations (PDEs) is presented. This methodology is a multidimensional extension of that presented in a previous work [Comput. Methods Appl. Mech. Engrg. 191 (2002) 3909]. The method proposed is unconditionally stable, by incorporating convection differencing schemes with the TVD property, and the grid is dynamically adapted so that higher spatial resolution is automatically allocated to domain regions where strong gradients are observed. The two desired properties of any PDE solver, stability and accuracy, are therefore retained. Numerical results for four test problems are presented which serve to demonstrate the robustness and cost effectiveness of the method.