Numerical simulation of a three-bed PSA cycle for the methane/nitrogen separation with silicalite

In this work, a three-bed PSA cycle for recovering methane from methane/nitrogen mixtures using silicalite is analysed by numerical simulation, including two equalization steps and a rinse step. The model employed is derived from conservation equations, considering assumptions widely accepted for these systems. The experimental adsorption isotherms of methane and nitrogen required for the PSA model have been measured up to 10 bar, and the mass transfer coefficients of these gases on silicalite have also been estimated from experimental data. According to the simulated results, it is possible to recover methane with pipeline quality in one stage with high recovery (87-96%) from mixtures with nitrogen content as high as 50%. This process has the potential of significantly increasing the adsorbent productivity with respect to the reported values for the same separation by PSA, and the theoretical power consumption is lower than the one reported using membrane technology. (C) 2010 Elsevier B.V. All rights reserved.