One idea that is being toyed lately is the use of a short bed of nitrogen selective adsorbent operated on a high frequency PSA cycle. A simulation study investigating the feasibility of such an idea will be the central theme of the talk. Departure from equilibrium and plug flow approximations in a high frequency PSA operation in a small bed will be assessed. Solutions of the model equations using FEMLAB as well as our own FORTRAN codes based on the method of orthogonal collocation will be compared and the experience with FEMLAB as a potential tool for PSA simulation will be shared. The validity of the Linear Driving Force (LDF) approximation for capturing adsorbate transport in the bidispersed adsorbent pores will also be evaluated by comparing with a more realistic pore model solution that assumes equilibrium in the micropores and allows for molecular diffusion in the macropores.